Joined: Jun 2010
Posts: 2,136
Likes: 1,524
From: Medford MA
Bikes: Ron Cooper touring, 1959 Jack Taylor 650b ladyback touring tandem, Vitus 979, Joe Bell painted Claud Butler Dalesman, Colin Laing curved tube tandem, heavily-Dilberted 1982 Trek 6xx, René Herse tandem
I don't think anyone's mentioned this yet, but my thought is that the dropout might be worn. I've seen them so worn from abuse (tightening nutted axles with serrated nuts comes to mind) in such a way that they are varying thickness, which might cause a hub axle or QR skewer to fail to "bite in" and might have a sort of "favorite spot" that the axle/QR slides toward.
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.