Encountering the workout erg-mode gremlins as well.
Kickr Core + iMac + iPhone companion app. Latest versions of Zwift and latest firmware for Kickr Core.
Background: When working out (and not in erg-mode) I sometimes experienced delayed feedback, sometimes substantial, between the wattage applied to the pedals and what the Zwift app registers (wattage, cadence). The best solution in my case was to register bluetooth devices via the companion app, which reduce the lag to around 1 - 2s.
Problem: When attempting to do a structured Zwift workout, there is a lag of around a minute or more between changes in target wattages and the erg-mode wattage simulated on the Kickr Core, i.e. it is completely impossible to do a workout because the the disconnect in values means the app will do things like increase the resistance even if you’re already over the target on the screen. (This happens even if the lag between pedal wattage and Zwift is minimal, so it is not bluetooth related.)
I’ve not had erg-sync problems in RGT cycling or Sufferfest, so I’m inclined to think the problem is on the Zwift end.