Locked shape suddenly shifted by one keypress step

TL;DR: locked shape in absolute coordinates suddenly doesn’t match the actual spot where it was originally cut, and it’s exactly one keypress to the right of where it was supposed to be; nothing moved on the laser

Hello all, I use LightBurn Core 2.0.05 on macOS with a Sculpfun S30 Pro. I’ve only been doing for a few months so this may be a stupid question, but I’m genuinely baffled.

Due to the S30 being open gantry, I occasionally make a throwaway cardboard jig. I make sure the honeycomb doesn’t move, use pins to keep the cardboard where it is, cut the hole I need. As long as nothing moves, the etching is perfect. I’ve done this many times.

Today however I found that somehow the jig on the canvas doesn’t match the physical jig. Nothing moved physically, and the jig in Lightburn is locked precisely so I don’t accidentally move it. Yet, for some reason, Lightburn thinks that the jig is exactly one “step” away from where it should. I tested this by unlocking the shape, selecting it and pressing the left arrow once, and the framing was (again) perfect.

The jig in the canvas never moved, as I was able to “rewind” the undo levels enough to see that it never changed. Further, I moved the head to a specific point by coordinates, etched a tiny dot there, then homed and moved the head to random spots. Going back to the dot’s coordinates, it was spot on. It’s not a general coordinate offset, it’s as if that specific object

The most confusing part is that everything was perfect for the first few engravings, then it suddenly started doing this. Restarting the laser and Lightburn don’t seem to have any effect. Opening an earlier version of the file also exhibits the same issue. It’s really as if I either moved the honeycomb, but what are the odds of moving it exactly the same distance as a single keystroke in a single direction?

I can just move the jig in the canvas so it matches again or cut it again, but I’m wondering how such a thing can possibly happen.

Thank you in advance!

Better than the odds of the laser frame, honeycomb, and template moving if they are locked down. Your description strongly suggests something got bumped about 3/16” or so. Unless you measured with a caliper, “exact” may be loosely defined.

My S30 Pro has the feet captured by a cutout glued to the table. The honeycomb has the same positioning guide. I can remove either and place it back in the exact (relatively speaking) location. The honeycomb frame acts as my final locator for the templates. So everything goes in the same place. That leaves me as being the only variable.

If you are wondering why the stilts, it is raised so I can get the RA2 chuck rotary under it. The white base under the honeycomb has a big hole in it, which is normally covered with an aluminum plate.

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