I have a Sharp Digital AR161 photocopier. It has just started with a problem in that when the copy paper is going through it starts to concertina up by the roller. Any suggestions on how to fix this problem?

Make sure the fuser rollers are turning, sometimes the gear either breaks outright or the key on the gear that locks it to the fuser roller shears off and the rollers will not turn proper. Mark the roller with a marking pen run, then see if mark has moved. If not more the likely the gear needs replacement.

Hope this helps...