And here is a race comparison (33 mins). The pedals average -12% power compared to the KICKR CORE. Not good…
How old are the pedals and do you ride them outside? Are the bearings still smooth? I have PowerTap P1s and they need to be occasionally disassembled, and spindles/bearings regreased. Currently in the maintenance box awaiting a maintenance session.
The pedals are only 4 months old.
Are you using pedal washers? If not I would try adding one to see if there’s any change. If you are, add a second one.
The Assioma Pro RS-2 pedals arrived yesterday. My first test against the KICKR CORE was a Zwift pre-race warm-up (19 mins of varied effort across all zones). My second test was a Zwift race (30 mins of varied effort across all zones). The power measured by the pedals averaged -8.3% and -7.4%, respectively, than was measured by the KICKR CORE. This is generally a little closer than the Garmin pedals (see above), but not as close as I would expect. During periods of high power, the measurements are more similar (<5% difference) than they are at low power (>10% difference), something also shown by the Garmin pedals (see above). It seems the main cause of the difference between the two brands of pedals and the KICKR CORE, is the latter substantially over-estimates power during periods of softer pedalling. This KICKR CORE was bought in July 2024 direct from Zwift, as part of the Zwift Ride bundle. It auto-calibrates regularly by itself, the firmware is up-to-date and the drive train is thoroughly clean. I’ll get in touch with Zwift customer support and see what they say.
you can drive yourself insane trying to get power meters to match. Kickr core +/- 2%, Assioma +/- 1%, plus drive train loss between the two… 5% difference seems “acceptable”
I don’t know what the drive train loss is on my Zwift Ride, but I’ve seen DC Rainmaker use 2 to 4% as a guide for such loss on trainers. So at, say, 300w beyond the drive train we would expect the KICKR CORE to measure 294-306w (+/-2% accuracy) and the pedals to measure 303-315w (+/-1% accuracy plus 2-4% loss via the drive train). That is, the pedals should mostly be measuring higher than the KICKR CORE, if the stated accuracies are correct. When my KICKR CORE is measuring about 300w during my tests, my Garmin pedals are measuring about 275w (-8%) and my Assioma pedals are measuring about 285w (-5%).
My advice is to choose one power source (probably your new assiomas) and use them as your primary power meter. I don’t think you will ever get them to match, and it sounds like you have made all the correct procedures to install and calibrate them.
Another possible configuration…
I can confirm that the problem I’ve reported in this post is due to substantially erroneous power data reported by the KICKR CORE that was supplied with the Zwift Ride. I know this because I have just bought a KICKR v6 for comparison, and the reported power matches perfectly with my Assioma Pro RS-2 pedals (see data below from a Zwift race earlier today), and both of these match well with my Garmin RS200 pedals. The odd one out from this bunch is the KICKR CORE, with its inflated power data, especially during periods of lower power. I’ve since seen that other people on this forum who have bought the Zwift Ride have had the same problem with the supplied KICKR CORE. If you own a KICKR CORE and haven’t yet tested its accuracy with dual-recording, it might be an idea to do so, if the data is important to you. Very dissapointing, especially given the cost of this stuff.
can I buy your old Kicke Core? 
Sure. It comes with a guarantee of increasing your FTP by 10%
thats why I want it 
You know that you can pair your power meter to wahoo trainers which will use this power reading for adjusting the resistance and then broadcasts it via BT or ant+?
A final update on this post. After some back-and-forth, Wahoo have agreed that the KICKR CORE is faulty and have agreed to provide a warranty replacement. That said, I do like my new KICKR v6, so shall keep that and will sell the new KICKR CORE when it arrives.
Yes. But the original problem was, I didn’t know if it was my Garmin pedals or my KICKR CORE that was providing unreliable data, or both.
I had the same issue with my Favero Assioma Duo pedals.
I borrowd two different sets of the same pedals from friends.
All three pairs of pedals measured within one watt of each other, while my Kicikr varied, but sometimes by a watt or two, sometimes more, it depended on the type of ride (workout, recovery, AdZ effort etc.).
So now I just pair my pedals to control my Kickr via the Wahoo app.
I have apples-to-apples between indoor & outdoor riding.
how did you test 3 pairs of pedals against each other? random curiosity
I tested three pairs against the Kickr.
The difference between each set of pedals & the Kickr was consistent under the same conditions (ERG, free ride etc).