I think unfortunately we are all coming to the same thought. I have noticed this in both Bluetooth on my phone as well as the ant+ setup. My son uses his phone as well. But using simple resistance in BT mode on my phone in the wahoo app worked. The one thing I have not checked is to see if the settings in wahoo stay in place if I power down and power back up outside zwift. I might try to use erg mode and just ride around this week when the weather goes south. Both my son and I tried to do a group ride last Saturday and zwift froze up and kicked us out.
I am actually afraid a zwift update in Mid December is what might have done this. I am not sure if the wahoo update is that new or not. We had huge issues with a wahoo snap a few years ago, so I am a little suspect sometimes of wahoo’s updates. I love the user friendly parts of wahoo products and the customer service is top shelf, but I fear sometimes stuff gets released without full testing. Anyway, we shall see what zwift says.