I've built up an Orange P7 from about '93-'94 with a XTR M952 rear mech. The problem is the rear adjustment screw does not sit on the tab on the dropout. This causes the mech to spin round and the upper jockey wheel hits the cassette. I refitted the mech a couple of times in case it was something simple, but the problem still exists. Having never seen this happen before, I can't figure out what is wrong. Any ideas would be helpful.