I am finding large discrepencies between my crank-based powermeter (SRM - calibrated before each ride) and my computrainer (calibrated before each ride with a 10-15 min warmup at ~150 watts and spin down test). In the past, using other platforms and Zwift in the past has resulted in a variance between my SRM and computrainer of 1-2%. The difference for the past 6 months or so can vary by as much as 20%. This typically happens at higher power levels (e.g., near the end of an FTP test above 320 watts) or on steeper climbs (>6 grades). For example, on the recent MAAP stage 3 climbs, Zwift was around 175-180 watts and my SRM head unit indicated 220-230 watts.
Do you have any suggestions to address this? It seems to result from slowdowns in wheel speed and overcompensating the resistance on the wheel. I would like to avoid buying a new trainer if possible
Thank you in advance.