Rapha Festive Workout "free ride" ERG fail

Hi

Had an issue I’ve not experienced on a workout where ERG mode seemed to limit my maximum output in a “free ride” section on one of the Rapha Festure workouts.

Workout was Rapha Festive 2020 “Free ride sandwich”

Workout was going absolutely fine and trainer was adjusting through each workout block as expected. I’d completed the first 4 minute zone 1 (50% of ftp) but when workout switched to “free ride” it held me at the maximum wattage of zone 1 (50% of ftp)? I didn’t change gear before hand but left it in same gear.

There after nothing I did seemed to break out of this. I couldn’t ride at the pace I wanted - even when the workout prompt suggested “60 seconds of maximum power?”. The harder I power the less resistance and easier it got to hold me at 50% of ftp. I tried ERG mode off/on. Stop pedalling and restarting but nothing would let me go beyond 50% of ftp.

What did I do wrong?

Using Wahoo Kickr Core, PC Zwift with iPad Companion. I haven’t done a spindown for a couple of weeks which I then did after abandoning workout. Could that have been it?