Is the axel protruding past the dropout? Even a tiny amount will cause this. If so a washer will fix it.
I've had a look at this, & no, doesn't appear to be the case. Something I didn't consider though, so thanks for the suggestion!
@GideonPARANOID started
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Is the axel protruding past the dropout? Even a tiny amount will cause this. If so a washer will fix it.