ERG mode watts too high

When I use ERG mode, my trainer (Bkool pro2) holds the power typically 20-30 watts too high. I use a Favero Assioma power meter to capture the power data. For example… in a workout I’m supposed to be holding 320watts, but the trainer will have an increased resistance, and hold me at about 350 watts. It makes ERG mode unusable. I’ve had other powermeters that worked flawlessly. I’ve been using zwift since 2015. Has anyone else experienced this? What can I do?

If you pair the Assiomas as your power source then when you do a workout in ERG mode it will use power match and adjust the trainers resistance to give you the correct power.

I’m using a single Assioma for the power recording and cadence and the trainer for control

Power should then be correct. if not then I suggest you do a support ticket with Zwift.