Cracked Idler Wheels 'N Apples

As Sumer in Calgary is coming to an end I’m starting to do more activities inside. I have two heatcores built they were working ok but the noodles were curling after a some time. On one of the reprap blogs someone had noticed a similar thing after lots of usage and drilled out the nozzle thinking it was becoming an oval instead of a a circle. Mine seems to curl but not initially which has started me to wonder if it’s not related to pid settings or something Else related to the new makerbot firmware 2.3 I think.