TLDR - tighten up the screws on the x axis rail or they might come loose and block the print head.
Discovered this when the printer made a loud bang when moving on the x axis. It was clear that it wasn’t moving fully to one side, then crashing into the right. It also then was out of position on the y axis too (most noticeably it was trying to wipe in the wrong location).
I didn’t spot the screw immediately as the angle I was looking from meant that the screw was hidden by the belt, so I thought the problem was with the belts.
I was only once I moved the print head by hand I realised it was hard stopping as I moved it to the left and, as I ducked down to see if there was any debris, noticed the screw standing proud of the rail (red circle).
It appears that not every hole has a screw and I thought I’d found and tightened them all only to immediately experience the same problem again as the screw circled in orange (not visible in pic) managed to fully unseat after a few layers of print - failed to cut filament when changing colour. Again this then messed up both the x and y positioning and required abandoning the print and re-calibration.
It’s now happily printing away normally.
