Garmin 520 and Kickr control

I am using my 520 to control the Kickr with workouts from Trainingpeaks. For longer duration intervals ERG is ok for holding a target power but when I get to shorter say 20s intervals it sets a target in the middle of the range and it hits a wall, which I know is what it should do. 

I can switch to Resistance during the workout but always flips back to ERG at each interval. Trying to reset to Resistance in 20s isn't doable. 

Can I change a setting so it stays in Resistance??