Mine does the same thing it’s the motor overheating there is a temperature sensor that you will need to by pass to avoid this issue

Here's the fix guys :

The motor driver power supply inside is overheating and will shut down until it cools to a lower temperature. I installed a small computer fan inside (1.5" square) and directed the air flow over the motor driver heat-sink and eliminated the shutting down problem. Now I can run continuous, I can swap batteries all day and it does not stop.