ERG mode turned on by itself

I just finished race 4 Crit stage and when a race is done, like usual I cooldown a lap or 2. Well as soon as the race finished and I got my banner awards across the screen I could hardly pedal on my Kickr V5. If I stopped the bike or slowed, then shifted mechanical to 21 or 24 I could pedal really easy then hard, shifted to 28 to pedal and still hard. I had to shift from front 50 to 34 to even pedal. I could hardly pedal the long downhill 3/4 way to finish.