V5 motors getting stuck

While building their robot, two of the motors belonging to a team from my school somehow managed to get completely stuck so that they could not turn at all.
The motors had been used before and had worked fine but when connected to the brain to run them, they did not move and drew the stall current of 2A and the shafts of the motors could not be turned by hand even when disconnected from the brain.
I fully disassembled one of the motors and found that the actual motor was stuck but when I twisted it with significant force, it became unstuck and worked fine when the brain was connected.
The other motor I managed to get unstuck by twisting hard with a gear on high strength shaft in a 600rpm cartridge.

Has anyone else had similar problems of motors getting stuck?

Yes this problem seems common for all of us with V5. Many times its unfixable so we contact VEX about the problem and get a replacement.

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Thanks for replying.
Do you have any idea what could have caused them to get stuck?
I have an idea that perhaps the brushes could have welded themselves to the commutator somehow.

Keep in mind that there’s two ways a motor would not be able to spin easily. The first is that the Brain’s motor port fries, so whenever you turn the motor it tries to convert the mechanical to electrical energy but cannot due to a short circuit. The second is purely mechanical. The first problem’s caused by the motor being pushed too much continuously (we once speculated static but we figured the logical problem is in regards to overcurrent of the motor). So don’t overwork any motor. In regards to the second problem its when either the motor gets overworked or the motor continuously pushes against a mechanical stop causing it to break a gear, most likely. The V5 motors are strong, don’t overwork them or they will break. Don’t make them push against a mechanical stop at full force or they will break.

I’ve seen motors get stuck when the planet gears inside the cartridge actually becomes dislodged and jam the whole cartridge. One of our teams had this happen to two motors.

I have a similar issue, but the motor only sometimes locks up. We took it apart and something sounds loose inside the motor in the v5 motor