Connecting to the wrong device

Myself and my partner zwift together regularly. She uses a smart trainer connected via Ant+ and i use a dumb trainer with my PowerTap Hub PM via BT and the companion app.

Recently my machine takes over her smart trainer and start feeding my watts to her trainer subsequently reducing or increasing resistance depending on the situation. Im not connecting to her trainer before we start in the pairing screen, it just does it every now and then but it does happen everytime we ride together.

Can anyone offer any advice on how to stop my machine taking over?

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Hi @Dave_Nicholson-DCV welcome to Zwift forums.

Shuji at Zwift HQ here. I see that you’re Zwifting on a Windows machine.

  1. Look in your Documents \ Zwift folder. In there is a file called knowndevices.xml. This is the file that stores what trainers and sensors you have paired with on that machine. It’s a plain text file you can open it in Notepad to see what’s in it.
  2. Go ahead and rename that file knowndevices_original.xml rather than delete it.
  3. Start up Zwift - when you do, you’re starting from a clean slate and you’ll have to pair up to your trainers and sensors from scratch.
  4. When you save and exit the game, it will create a new knowndevices.xml file and that will cause it to remember your freshly-paired sensors.

Let’s dig a little deeper. Do you and your partner use different computers to run your own Zwift sessions from? If so, which operating system does she use?

If you’re using the same Windows computer (and just don’t Zwift together at the same time): part of the problem might be that the game has both of your trainer setups remembered in the one XML file. The game is not making a distinction between two riders each with their own trainer vs for example, one rider who has a road bike and a TT bike set up on two different trainers.

The “correct” way to solve for this is to have a separate Windows login for your partner. She would log into Windows as a different user. Then she’d log into Zwift, which remembers her setup in her own knowndevices.xml file that wouldn’t get confused with yours.

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So i renamed the KNOWNDEVICES file as stated, and reconnected to my devices while hers were all turned off. 3 minutes into our indervidual sessions, my PC still auto connected to her controllable smart trainer. I pressed A and unpaired, but a few mins later it did exactly the same thing again.

We both have aa training session on wednesdays at 6pm. last week she had to stop all together because of this issue, and now this week i have had too.

Whats going on?? Why doe the game auto connect.

The game auto-connects to save you the trouble of having to manually pair every single time you want to ride. Even in multi-rider households, that convenience should work as intended if each person uses a different computer.

Clarification please: What things of hers were turned off? If her trainer was powered off, I’m confused how your computer managed to pair to it?

Would you please give us a breakdown of what’s in the room, and how you are trying to connect them all?

Your setup:
Trainer brand / model: Which “dumb trainer”, please?
Power sensor: PowerTab Hub via BLE
Speed sensor Add-on to bike?)
Cadence sensor: if any
Computer operating system: Windows 10, I’m assuming.
Zwift companion: (used as a Bluetooth bridge, or no?)

Her setup:
Trainer brand / model: Which smart trainer, please?
Power sensor (built-in to trainer, or add-on to bike?)
Speed sensor (built-in to trainer, or add-on to bike?)
Cadence sensor (built-in to trainer, or add-on to bike?)
Computer operating system:
Zwift companion: (used as a Bluetooth bridge, or no?)

We have also been having the same issue. When I go onto Zwiftalizer it show both trainers as connected devices to one computer.
When riding we can feel efforts change as it jumps from one trainer to another.
This has never been an issue before and only recently started happening.
Our setup
Tacx Neo 2T
Separate Ant cadence sensor
Power / Speed controlled by Neo
Separate windows 10 computers hardwired to network.
Communicating to trainers via Ant dongle

So ive even now gone to the extreme of removing zwift from our machines and reinstalling with no joy.

I have just done a race wwith a group of friend in meet up and 15mins into the meetup, my machine randomly connected to my partners smart trainer which obviously i wasnt on, so my avatar just stopped.

My equipment are as follows;-
Trainer;- Tacx Blue Motion (dubm trainer)
Power sensor:- Powertap G3 hub based power meter
Cadence/speed:- Trek DuoTrap 2
Computer:-Windows 7 professional
I use a Ant+ dongle to connect but have used Companion and bluetooth before and still does the same

Her setup
Tacx Flow Smart T2240 taking power data from this also
Garmin speed cadence sensor
Windows 8.1
used with a ANT+ dongle again. She has never used the companion app to connect her devices

This issue is making Zwift useless to us as we work similar hours and so end up training at the same times.

Also managed to figure out that this issue began on the 7th May.

There was an update that day before we did a meetup race together. On that mattup was the first time we experienced this isse, and now have it everytime we train at the same time.

@Dave_Nicholson-DCV this issue might be related to another bug we’ve been working on. Not 100% sure it’s the same thing, but there’s a patch for it in this next game release, that’s due this week. Fingers crossed this resolves your situation.

Hi, I am also having the same issue. I just bought the Wahoo Kickr core and did my first ride today when my husband was riding on Zwift and even though I was connected, it kept disconnecting and I wasn’t going anywhere. We restarted, I started first, then he couldn’t sync (just using wahoo sensors on an old trainer) and hence couldn’t ride today. Something very odd happening. Hope it is just a bug. Both of us are using bluetooth to connect and both have separate accounts and PCs. This happened before the upgrade this morning then continued after.

Alas I thought it was sorted, but still not.

Tonight my computer connected to my partners trainer and messed both our sessions up.

What is going on? Why the auto connect?


Since you have already taken the step of resetting your knowndevices.xml file, it may be time to try something more drastic by nuking everything Zwift-related and reinstalling from ground zero. This will also wipe out any personal bests and custom workouts you have stored on your computer. If you and your partner ok with that, then in Windows Explorer:

  1. Search for “Zwift” and delete any folder or file that comes up.
  2. Manually download the latest game version from
  3. Reinstall.

@Dave_Nicholson-DCV by chance, are either of the devices on which you are running Zwift connected via wifi? If so, you may want to try updating your router firmware, as well as changing your router settings to use a specific channel, instead of searching for the ‘best channel’.

Had similar issue both me and my wife use Kickr Snap and when we started up, the Zwift just connected randomly i.e. my PC to her Snap or her PC to my Snap, etc. We had to manually unpair and connect to correct Snap. I changed knowndevices.xml, same. Luckily we didn’t have many problem during in-game.

We used to re-install Zwift couple months ago and so don’t want to do it again since still not impact in-game. Won’t there any way to check in Zwift code, how it connects to device not in Known list rather than uninstall and reinstall.

Hi @shooj

I saw your post about how @Dave_Nicholson-DCV could go into the knowndevices_original.xml file to help him stop pairing to the wrong device with a windows environment, but I’m having a similar issue but using Apple TV 4k’s.

My girlfriend and I both have TACX Neo 2T’s with Apple 4K’s right next to one another and no matter what I do, only one iPhone with Zwift companion will see both trainers. I tried removing power from one trainer, then getting her trainer and HRM connected and going into Zwift, then trying to connect my trainer and connect, but what happens is both trainers will show up on one iPhone and there is no way to say “forget device” so that I can pair it properly.

Is there a way to get this to work where we can specifically tell each companion app to only pair to a specific trainer thereby it’s discoverable by the other iPhone with Zwift companion?

I tried disabling bluetooth on each phone pairing one trainer then hoping I could pair the other to the second iPhone but they just kept ping ponging where both trainers would pair to one Zwift companion vs. the other.

Apple locks down the tvOS operating system so you can’t use the knowndevices.xml file.trick as you can on MacOS.

Closest thing you can do is uninstall the Zwift app from both Apple TV’s and be careful about which unit pairs to what trainer. Simplest way to achieve that might be to power off the trainer and iPhone that’s not being paired at the time?

No, because it’s not the zwift app on Apple TV that’s pairing to the two trainers. It’s paired using the Zwift companion. The problem is in the bluetooth section of the Zwift companion there is no way to tell it to “forget a device” thereby freeing it up to be paired to the other iPhone/Companion.

Sorry not helping you but…
Hi how do you do this? I would love to try it on the PC.

Having the same issue. Using two Apple TV’s and the companion app to pair. We have been doing this for two years and never had this issue. Seems like it started within the last few months.

However previously my wife was using the Apple TV to pair and not the companion app, which capped her connections. We have since gone back to this and try to pair her devices first.

If I pair first with the companion app it grabs every Bluetooth connection available and won’t let go even after leaving the pairing screen and starting the ride. A few times I have even noticed it paired our neighbors baby monitor. Beyond this being a very frustrating user experience, seems like a potential security issue.

@shooj I too am having the same issue. 2 of us at home typically ride at the same time. Both of us have 2 different Win10 machines with ANT+ USB A device & Bluetooth (built in). We both prefer ANT connections when the same sensors shows BT & ANT. Both have latest zwift installed. I have latest gen Kickr Core, Wahoo Cadence & HRM. She has Garmin ANT-only HRM, Bontrager duotrap Cadence & Wahoo Speed sensors. Classic Fluid 2 Cyclops trainer. No power meter.

We’ve experienced issues since November, ever since I got the Kickr and she got my hand-me-down prior classic setup. Every so often one of our rides gets messed up mid-ride - either my watts drop to 0 or hers go wild (I have higher ave w/kg). If my trainer is turned on when she launches Zwift she always sees a connected power meter, and controllable trainer. She always unpairs them on the initial sensor screen. She only connects HRM, cadence, and speed sensors, as outlined above.

Today I tried two more things that added to my troubleshooting and frustration level, eventually finding my way here:
I did an indoor ride with all the sensors and Kickr trainer connected to my Wahoo Elemnt Roam computer in virtual route mode.
No Zwift at all. Halfway through my ride, my watts on the Elemnt dropped to zero, Elemnt auto-paused while I was throwing a consistent 200+ watts at it. Kept pedaling, hit manual resume, and ~10 seconds later my watts were back.
Same thing a couple minutes later.
A few seconds after that, she walks into the room saying her zwift kept connecting to my trainer, so she just stopped altogether.

Eventually I finished my ride, upset at her and noting the real issue was the tech, and as the IT guy of the house I tried to fix. Had it worked, I wouldn’t be writing this long post…

After closing Zwift on her machine, I went to prefs.xml, cross compared LASTCONTROLLABLETRAINER and LASTPOWERDEVICE, and as I’m sure you already know, they were the same. I left the elements in the XML, but changed the last 4 digits of each to 9999. Save file. Restarted Zwift (with my trainer still turned on in other room) and eventually my trainer auto-connected again. Frustrating.

Exit program. Open prefs.xml. Deleted the two above elements and LASTTRAINERDEVICE while I was at it. Save and close xml. Open Zwift. Manually setup her classic trainer again. Again my trainer auto-connected. Super frustrating.

Exit program. Open prefs.xml. Deleted the elements again. Save and close xml. Renamed knowdevices.xml to OLDknowndevices.xml. Open Zwift. Manually reconnect everything again (took a while to get cadence & HRM to pair, kept toggling between Not Connected and ERR for cadence, etc) Once again, my trainer eventually reappeared. Beyond frustrated.

At this point my 3+ months of troubleshooting has led to this longwinded, but hopefully helpful to the devs post. I’m open to just about anything at this point - and yes, we’ve both already gone through the whole uninstall Zwift, restart, delete everything from Program Files + Documents reinstall, etc.


I have also just started experiencing the same problem. My husband and I have been zwifting together absolutely fine for 4 months. Yesterday for the first time this problem occured and trying again today the problem remains.

Both using our own Kickr core, he is connected to laptop and me to ipad.
Pairing screen shows us both connected our own correct devices for power, cadence and controleable.
His is fine no problems.
The resistance on my trainer is adjusting to his ride instead of mine.
My avatar is riding my power and cadence but not it its road/course instead I having to adjust according to where his avatar is in the event.

Solution tried:
We have tried unpairing and repairing the devices and uninstalling and reinstalling zwift app on our devices.

Is there anything else we can do other than not ride at the same time?