I continued my search through the archives after posting my question to you. Some have diagnosed the problem as the paint on the needles getting a bit gummy and sticking to the pin. They say the problem is worse in cold weather - something I've noticed myself. Tried banging on the dash today and the needles came un-stuck. So I think I'll pull the cluster and see if I can clean the paint at the point of contact. But, I don't think I'll do it this weekend...

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Dave
1995 C280
1999 Triumph Daytona 955I - my speed fix.
1982 300TD - Gone, but not forgotten.