Is it only on large inclines or does it happen in all types terrain.
How the Das-kit controller and display works is that the pedal assist will power you to a certain speed based on the PAS level and then cutoff.
What I think is happening is that at very steep hills it is reaching it's speed limit and cutting out, then you are slowing down and then it is providing assistance as you went below the cutoff and the cycle repeats.
I would increase the PAS to the highest level and see if the same issue occurs. If you are already on the highest PAS then there might be something else.
Another thing is to check is to go into the settings of the display. It varies by model but on my bike it was 8088. When you cycle through the settings there will be one for eco, normal and power. Try putting it to power and see if it is making the climb.
Edit: Here is a video showing the procedure.
I would more doubt the controller than the motor.