In the past week, my Tacx Neo started to produce rapid-fire resistance changes at startup. In the first 3 minutes of a ride the resistance would come on and off very quickly. The trainer was unrideable. After 3 minutes the resistance would settle in, but would still act very strange. The resistance on hills was random but mostly felt like I was riding on the flats. At times when it got steep, it felt like I was riding up hill then down hill, back and forth every 10 seconds. Also on the flats if felt like I was riding down, -2% or so. When I ramped the power up over 300w, the resistance would also reduce on all terrain. It felt like this random ERG mode gone wrong.
I tried everything. Turned off all devices. Turned off bluetooth. turned off phone. Moved Ant+ to within 20cm of the trainer. Turned off fan. I was able to replicate this with 4 computers, 2 tacx neos, and 1 ipad. I uninstalled and reinstalled zwift… Support was not able to help me.
The problem was my Wahoo Element Head Unit had the Neo as an added sensor. I use the Wahoo Element to monitor power of the Tacx so I can do intervals and use the lap function. When you add a sensor on the Element you can add what is called the “Neo”. Well it turns out that means the Wahoo Element is CONTROLLING not monitoring the Neo. There is a different sensor you can add that simply monitors power on the Neo. Once I removed the ability for the Wahoo Element to control the Neo, all the crazy resistance changes stopped immediately.
So if you are experiencing a problem like described above, make sure your head unit is not also controlling your trainer.