ERG mode during TTT event

On last 2-3 mouth, most of the time during an TTT event, my Tacx flux s trainer are on ERG mode.
Yesterday it was during my warm up, and i was in free mode, not in a training activities. And it stay on ERG mode for the TTT event after.

As we not having anymore the choice to select that mode, what can i do to solve this issue?

The trainer as the last update, i use an ANT+ doggle and bluethoot connection. I try to calibrate with the Garmin app and with Zwift without any change.