Offsetting in print over long print times

[qmaker 29]

Hi guys, After the um2 to um2 plus upgrade my prints have been quite nice. However, I have been doing smaller prints. Recently I tried printing at full build volume for a few different models. The print gets 10 hours or so (time is not relative here, just along way into the print) into the print and then there is a large offset and it continues to print for several hours then large offset again. I tightened all of the set screws at the pulleys and even marked the pulleys to see if I could see if any were slipping. Don't see it happening. The print is not slipping on the bed it is fully adhered not moving around. Any other suggestions of what to look for next?

It is only happening in the Y axis right now. Is my belt perhaps slipping. Unfortunately, I have yet to be near the printer when it occurs so I can't catch it in the act.

Thanks,

Q

[qmaker 29]

OK, so I was able to get most of it to go away, but I still have one shift in my latest model arghhh. Must have occurred around 18 hours into the print, and I thought I had it taken care of. I tightened all of the set screws on all of the pulleys. Maybe my belt, or maybe there is one that just slips a bit still even when the set screw is "tight" I will retorque all of them again and post back whether it solved it, just in case anyone else experiences the same issue.

[Titus 170]

It looks like this right?

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#shifted

Not like this

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#leaning

See links for fixes Hope it helps!