Decided to go through this R1 beta/first(?) since I have found too many little items "loose" or questionable. Found the X -axis belt riding up on the motor drive pulley "guide" so adjusted that. Found at the other end, idler, the belt is riding against the rear guide. I attempted to resolve that by adding a washer or three to move it toward the back of the unit. That did not seem to help any. So I removed the rear guide, just a large washer it appears and found the belt will just ride off the bearing completely as I move the carriage. I will play a bit more to see if I can resolve this, but perhaps someone has seen this and has a simple fix.