I’m using a Wahoo Kickr and a Macbook Pro on the latest OSX. Haven’t had any issues for many months. All of a sudden I cannot use ERG mode and occasionally the trainer will go to something crazy like 700w and I can’t even turn the pedals.
If I use my Wahoo app and manually control the resistance, it comes through to Zwift perfectly and the correct numbers display. On my legs it also feels correct.
So I’m not sure what Zwift has done, but the ERG mode is broken 
hoping you can fix it soon.
I’ve reinstalled Zwift on my Macbook and that was no help.