Does the print that work well always work well? Do the prints that don't work always fail at the same time in the same way? Answers to these questions would help us troubleshoot.
That your printer always runs to an edge is suspicious. Is it always the same edge? A loose wire to a stepper could cause your motor to only move in one direction.
Good luck. Keep reminding yourself that the troubleshooting is half the fun. (It's what I had to do.)
Brad
