| Seen it before with hard anodised drop outs and certain QR skewers, the skewer should have knurled bits which grip the paint on frame which an XT should have, if the frame is hard anodised or the drop out design means the skewer clamps to dropout not frame that can cause it. We went to a harder dropout on one model because people complained the hanger bent too easily, resulted in a few riders having same problem, put power on and wheel pulls over. it can also be a difference in dropout dimensions, they are usually about 10mm +.2 but some are bigger than that, occasionally you'll get a Hope hub axle that doesn't seat exactly. I'd be surprised if an S works bike was like that though.
If it wasn't designed for discs and you run that adaptor that might also stop skewer clamping up, not sure though as its a long time since I saw one. AIR there is a different skewer cap on it which recesses into the arm, not sure what the arm fastens against on frame though. might be worth giving Hope a call, their customer service is excellent.  | 
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