They're replicating

Last night I did about the 6th full teardown of my RepRap's Y axis - the brass bushings that MG uses to slide are EXTREMELY intolerant of misalignment - I found that even a small fraction of a turn (maybe 1/50th turn) on one of the smooth rod clamp nuts resulted in binding. It's very smooth now though, and I made sure to get things tight.
I was working on the Y carriage because I thought of a great plastic bushing to print up that makes the glass clamp work way better than the rubber gaskets I cut originally - it's much easier to adjust now.

I've started to print the plastic parts to build a second printer. Unfortunately I got about 3/4 of the way through a beautiful print of a frame vertex this morning and as you can see, suddenly the printer jumped about 10mm to the left. This happened to me last night too except it lost 10mm in both X and Y. This can't be caused by mechanical issues, it has to be electrical.

My best guess at this point is that it's a communications issue, so I'm starting the print over, this time printing two at once but printing from the SD card so communications will not be an issue. We'll see if I can print a bunch of parts without issue.

I'm having to pull together parts from a variety of places since I'm planning on using linear bearings, which changes a lot of parts, metric smooth rod, and non-standard endstop switches. Also someone posted a new Z-motor mount variant to Thingiverse this morning that I think is quite clever and I'm going to go with it.