I had a nightmare on that one last night. My Kickr was no altering until 30 seconds after the fact.
Funny you should say that, I had problems too and couldn't quite track it down. I had similar to you, but the resistance never kicked in, just slowed me on screen... So I was spinning away near the top of my 11-28 assette (in my 52T) on those ramps barely turning 220W.
I saw 1 other comment in the ride about someone having issues. Then have also seen 2 other rides from friends (+1 random ride title from same ride as me) who also had problems.
After all that I'm not convinced there's not a Zwift bug. Maybe due to the number of riders in these events.
Not that there should be! Looking at my data earlier the ride I was in for 2019 had 2300+ starters, with no issues, the one this week had less than 400...
I had to have a toilet half way through too, but I'm not that fussed where I placed just on there to keep the mind ticking over.
Managed to get an extra month off the code
@Marzipanogram gave me as the code expired after a month, Zwift looked into it and just re-applied a whole 3 months. That should keep me going until the nicer weather! Unlikely to use the turbo much after April unless it's really bad.
I've used other stuff as distractions before (like watching rugby while just spinning away) but much of the time now there's so many group/training rides on there I'll just do those instead. I don't seem to need a distraction anymore on Zwift - the routes and landscape seem to be enough visual distraction for me, music is generally enough other distraction (currently Hardstyle, Dutch Techno & a bit of Jump up DNB). But I'm so low on mileage (+ time) I have no time for 'junk'/recovery miles anymore, I'm constantly battling to get volume in with the time I have.