I disagree with the idea that a thread repair solution like a Helicoil is not effective. The approximately doubling of the screw to female thread engagement area makes for a very much stronger fastening. There are several alternative systems on the market but the Helicoil design is probably more likely to be available at any decent sized fastener store. The required inserts, insertion tool and tap is not a five and dime purchase but compared with a replacement motor it is a bargain. And fix all of them while you are at it. Be proactive.
For what it is worth, when I build apparatus for highly stressed environments such as racing cars and aviation related designs, I build thread reinforcements of some sort into the design.
Mike
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