Well chain and cassette are new. I don't think crank is worn. It's my backup one I use when my srm dura ace out of commission (which is the case now). Yeah rear derailure is adjusted, and everything is spinning fine. I never had this issue with my dura ace crank. This happens with a different rear wheel also, and different cassete, so not a wheel issue. I got a 1mm spacer, going to try that...