@Battosaii it’s been my experience that every motor has that problem eventually, and using Loctite 290 helps but only prolongs the failure. But there are ways to get around that.
I’ve been pinning my motors with either 1) roll pins, 2) keys, or 3) dutch pins. The dutch pin and roll pin work better than the key way as they hold against slip in two axis instead of just one. The dutch pin (3) seems to be the best.
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roll pin
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key
- dutch pin