Erg glitch

I am using a kickr v5.
I am using erg mode workouts such as those found in “8-12 week ftp builder”

In 3 second average power mode everything works fine but if I go to to Zwift settings and switch to instant power mode my avatar wont move even though it reads my cadence my watts remain zero and I cannot start the workout. The only way to fix this is to switch back to the 3 second smoothing mode and then everything works fine.