This is not in workout mode.
My last two rides (races) had to be abandoned due to my smart trainer losing power over the top of hills when the road flattens. The difficulty would increase so pedaling becomes too hard and the watts rapidly decrease despite how hard I try and pedal or if I shifted down. (I have submitted a ticket for this)
I had another try today and something else happened. In free ride mode there were no resistance changes at all. Pedaling at a steady cadence though, my watts would still fluctuate as the on screen gradient changed - but I didn’t feel any change.
EDIT: Connected via an ANT+ dongle and FE-C options selected on the pair screens.
I have been using zwift for 8/9 months with no problems of this nature.