I have an angle that people might want to consider. I’ve been plagued for this for years now. It’s always at the start of a workout and if you can somehow get past it you’re fine. So my theory is this - the cause of some of these issues (probably not all but some) is the issue raised here:
(Can’t post a link in this reply but google “Zwift Stuck in workout mode” and it’s post 82102)
Because I noticed I was in this state on a workout and trying all the usual maneuvers and then at about the same time - the problem went away at the exact same time that my HR monitor re-paired. Which is to say that very often I pair up my HR monitor but then because I’m not warmed up yet (I can warm up inside the workout) the HR monitor drops out - this happens quite often. So I thought OK what if the HR monitor dropping out can lead to this problem.
And in the above linked report that’s exactly what happened. And the last two attempts I made sure that the HR monitor didn’t unpair (just by pressing the monitor against my chest the whole time) and the problem didn’t occur.
It would be good if people could check and see if this is at all a plausible cause. And if Zwift could try to reproduce in their test setups.