Love the Ikea lights.
I have the same ones on my printer and they are great.
I can only offer a few suggestions given that you seem to have covered all the bases.
I hope that these may help you.
First, have you tried re-slicing the model?
Save it as a different file name.
Especially if operating from an SD card, the gcode file can become corrupted.
SD cards are not as reliable as they seem, and some brands are definitely worse than others.
Also, some brands may be more compatible with the controller firmware than others timing-wise.
If you are operating from a computer via a USB connection, check to be sure you don't have a screen saver or other software that might interrupt the data flow.
Second, have you checked to see if there is something loose or intermittent in your echains?
If this is a random error that could be the problem.
If the shift is always in this exact same height though, that is pretty unlikely.
I didn't like the tighter bend on the X-axis chain and spaced mine up a little over an inch to make it bend more like the Y chain does.
Third, try swapping the step driver board on the offending axis with another one.
Re-tune the drive currents as necessary of course.
See if the problem follows the board.
Fourth, reload the firmware onto the controller.
Perhaps it is getting hung up at some point or other, or perhaps it has some bug in it.
Those are the things I would try if my printer were doing this.
