Fifth generation Wahoo kickr running on PC.
Erg mode disables during an “attack” segment of the workout rather than increasing to match cadence.
Had no issues before updating Zwift app this morning, seems to be related to update if I was a betting man.
You didn’t mention which workout you were using, whether or not you were in a group event, or what constitutes an “attack.” If the workout was designed with a specific power deliverable and not a “free ride” segment, and you have done a power reset/troubleshooting of your KICKR, I would put in a support ticket with Zwift, providing as much supporting information as possible, so that data can be reviewed.