how old is the cutter? i googled roland pnc 1210 and found a couple of links to people with problems of tension arm being out of whack. but problem sounds like that or pinch rollers. something that has to do with the feeding process. if the vinyl lifts off the bed of the cutter it could be the tension arm. here's a link to roland support for cutters:
Roland ASD - Cutters
set up an account and post your exact problem on their forum. i know one of the tech guys (dana) monitors this forum once in a while. maybe you'll get lucky.