The Y and Z axes each use two end stops to home the axes. If you find that over time the axes run out of alignment, you can apply a “soft” offset to the end stops to square the axes.
Pick a point of reference and measure the distance between the reference and the physical axis on the left-hand side when it is homed. Pick the same point of reference mirrored on the right-hand side, and take the difference between the two values.
The offset value can be entered using
M666 [Ynnn] [Znnn], where
nnn is the offset value in mm.