Having opposite terrain effect in ERG mode...

Riding with a smart trainer, (Wahoo Kickr Power, latest gen).

When I’m riding in workout mode, I would expect the resistance to be stable during a fixed watt block. However, I’m experiencing an opposite terrain effect when in ERG mode. Meaning when the terrain enters a downhill, I feel an increased resistance in the trainer, and opposite, when in uphill a slight decrease in watt. The watt numbers in the HUD stays stable as expected. My guess is that the change I feel is somewhere in between 5 and 10 watts.

Now to some pure speculation from my side. It is as if instead of turning off the terrain effects in ERG, there’s an extra layer of code that is tasked with the job to counter the terrain effects, and that piece of code is not doing the exact opposite to the SIM terrain effect part.

I’ve taken the trainer out of the equation as that one is not aware of the terrain, that knowledge must be only in the zwift sw.

side note. One could believe that this is all in my head, (I too believed so initially), but I’ve played around to trick myself by riding blindfolded, with someone standing next to me, and I called it every time on the spot when an uphill or downhill came. Still in ERG. I do also notice it on the pulse.

Could this be a bug, or have I screwed up some setting?

I have experienced the exact same issue as you are describing, as well as a few other people. There is another thread on here where this has been discussed but to my knowledge no answer has been given by anyone on this issue.