Dirt turns into quicksand, impossible to ride

I’m on a Gen1 Kickr, ATV. In my meet up today, I experienced an unusually huge decrease in speed (such that I couldn’t hold the pace) once we hit a dirt section. I was using a road bike in the game (Venge, Zipp 808s), but this was much more than the normal 4-5 kph loss you normally experience when going from pavement to dirt. Thinking it was my trainer, I did a spin down and also hard reset of my trainer. Neither worked. I quit the ride, started a new ride, and found the same thing… descending into the jungle loop, I suddenly went from 40 kph to 14kph while maintaining the same power going downhill from pavement to dirt.