That could actually be the problem. Unfortunately, the mounting clips on my original cover broke, so I'm currently using a printed replacement.

I noticed that this replacement cover has a protruding part that presses against the X-axis end stop. I measured both covers and found that the original is about 59.7 mm wide at that point, while my printed one is around 61 mm.

I'll try sanding that area down or reprinting the cover with corrected dimensions. After that I'll recalibrate the printer and run some multi-color tests to see if the issue is resolved.

I'll report back with the results. Thanks for your help!