<p>I've noticed that after my Anet A8 completes a print, the right hand Z mount ends up 1-2&nbsp;mm lower than the left, even though I make sure both the left and right hand Z mounts of the X-axis are at the same height before switching on the printer.</p>

<p>Does anyone know what the cause of this might be?</p>

<p>I'm guessing something is causing the right hand Z to skip steps. I can't see or hear any obvious mechanical issues. I checked all guide and threaded rods were straight before assembly.  </p>

<p>Could it be a faulty stepper or control electronics?</p>

Try winding the Z axis all the up and down a few times using the front panel controls. Does it still go out of alignment? Is it out of alignment at the top? Does it come back into alignment when you wind it back down?
The principle is: if you have a dodgy motor drive chip, or a mechanical fault, it will skip some steps on the way up and the two motors will be out of synch. Then, on the way back down, it will skip an (approximately equal) number of steps and the motors will return to something resembling similar places.