Motors not spinning at full speed

We were test-driving our robot, and it was working fine, but 10 minutes in, the 2 right motors stopped spinning at full speed, even when they had no load. I couldn’t see anything wrong with the gear train, and neither of the motors felt hot. Does anyone know what is happening?

For a drive train, if there is a lot of friction in the wheels/gears, that causes a lot more stress on the motors and after a lot of use can make them over heat and spin slower and weaker. Overheating is common in drive trains so making sure there is the least amount of friction as possible is important.

It was probably overheating or it could be your battery was low which would decrease voltage to the motors. Try it again after some time and see if that fixes it.

The rest of the motors were working fine, and none of the motors were even slightly warm.

I agree with this because with more friction and heat, it can cause the motors to slow down, even if you did nothing to it. Also, how old are they? They could just be getting worn out, happened to our robot.

I have no idea how how old they are.