Motors gone by the sounds of it.. ive heard motors do that sound before. Even my old 3m sencil maker made that sound i lubed the bear and it was good after that.. but you cant lube the bearings in the that motor.. i would take apart and make sure everything is lubed how it should be then see. If it still makes the noise then swap out the motor bolt if you have another. You could spin up the motor bolt out side of the body to see if it makes the noise with no tension!! But i think its the motor.

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