One side of Y-axis offset during carve

I am having an issue where – after a long carve – the right side of the Y axis ends up somewhat shifted compared to where it started.

When I travel to Y=0, the left side is consistently ~2mm from the edge. This is immediately after homing and after a long carve.

After homing, the right side is also ~2mm from the edge. However, after long carves (several hours), I find it offset. I went to Y=0 at the end of a carve and found it <1mm from the edge:

I re-homed, ran the same exact carve again, went to Y=0, and found it nearly 5mm from the edge:

What is the most likely cause of this? Since this is an Elite, I assume skipped steps aren’t a possible cause because it’s closed loop?

It looks like chips stuck in your bearing from the pictures you sent. remove them and try again see what happens

I’m not understanding how a few chips would cause this? Even if it got stuck, shouldn’t the closed loop either compensate for it or trigger an alarm? It moves very smoothly, I don’t get any jerkiness. It just accumulates some during the carve and I clean it off before the next carve.

I’d check the motor coupler on the offending y-rail. When I was calibrating my Elite Journeyman after upgrading it, I discovered that a Y-rail coupler was loose on the pre-installed side. Following that discovery, I went through and checked both sides of the couplers on ALL axes.

I think that may have been it! Definitely had a few loose screws on the couplers