Hello,
I bought an Ultimaker 3 one month ago and I have a constant problem of jamming/gindring in Printcore AA with PLA. All 2 hour long prints are half done because of this.
Actually, the filament is stuck because of an increase in diameter from 2.85mm to 3mm around the Printcore. Friction in boden tube, retraction prevented, grinding in the feeder, filament jammed.
That makes me quite astonished because I haven't changed anything in the Cura profile, nor on the printer. I never had a problem like this on Ultimaker 2+...