Since we are spitballing the issue, I would venture to guess there is some binding somewhere. Once the steps are skipped it is skipped for good. See if you can spot any binding in your movement. In my printer there is some very slight binding when the carriages are nearly at the home position. In my case I will try some sand paper or increasing tension on the rods to cure it. Also keep in mind print speed, the slower the printer moves the more torque it has, the faster it moves the less torque it has. Can you try to print at a slower speed to confirm the notion. If at slower speed there is no shift or the shift is lower, you have a binding issue.
I am using 20tooth pulleys on mine, I do not see an issue with shifting layers. Although the head of my printer is very heavy in comparison to most. I have mine sandwitched in aluminum and am using aluminum plates to hold the j-head. I suspect around 50% increase in weight.
I am using 20tooth pulleys on mine, I do not see an issue with shifting layers. Although the head of my printer is very heavy in comparison to most. I have mine sandwitched in aluminum and am using aluminum plates to hold the j-head. I suspect around 50% increase in weight.