I've tried replacing the batteries thinking maybe I had a bad set but it is no use

I purchased 2 of these units. One to use with salt that I have no issues with and another for pepper which I've determined is unusable. I put fresh batteries in the unit but the thing refuses to crush the pepper beyond a piece or two before jamming and ceasing to grind. I then have to unclog it and hope that it works. I've tried replacing the batteries thinking maybe I had a bad set but it is no use. I'm not sure if I just got a defective unit or it's just not strong enough motor.

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