CNC router occasionally makes jarring noise and home jumps when it does this. Help!!

[EddyCurrent]

On the second photo it looks like it jumped then came back into line again, did it do that itself or did you intervene and correct it ?

Is it direct drive or via toothed belt ?

[Jonathan]

I think in the second photo it jumped twice by different amounts, as it's not gone perfectly back into line.

It could just be the Y-axis motor is very occasionally stalling. I'd try running this code to test it more thoroughly and report back.