What Does This Error Mean?

Prusa layer shifting is most often caused by loose X or Y axis belt tension, or the print head colliding with a warped print or stringing. Check belt tension with Prusa's built-in belt status test and tighten if needed.

Affected Models

Prusa MK4
Prusa MK3.9
Prusa MK3S+
Prusa MINI+

Common Causes

Loose X or Y axis belt — skips steps when the motor reverses direction
Print head collision with a warped print edge or stringing blob mid-print
X or Y axis stepper driver current too low, causing motor step loss under load
Too high a print speed — momentum causes motor steps to be skipped at direction changes
Debris or binding on the X or Y axis linear rails or rods

How to Fix It

Check belt tension using the Prusa LCD menu.

On MK3S+ and MK4, go to Support > Belt Status on the LCD. The value should be between 240–300 for both X and Y axes. If below 240, use the belt tensioner adjuster to tighten the belt — the screw is accessible from the ends of the X carriage and Y axis.
Reduce print speed.

Layer shifting from motor step loss increases with print speed — the motors cannot overcome inertia at the direction change point. Reduce your print speed by 20–30% in PrusaSlicer. If shifting stops, increase speed in smaller increments to find the stable maximum.
Inspect X and Y axis rods and rails for binding.

Manually move the X carriage and Y bed by hand with the printer powered off. Movement should be smooth throughout the full range — any sticking or rough spot indicates a dirty or unlubricated rod. Apply a small amount of PTFE lubricant or Super Lube to the smooth rods.
Check for debris under the print or in the axis path.

A small blob of stringing or a warped print corner can physically stop the print head mid-move, causing the motor to skip steps. Inspect the model for warping in the first few layers. Ensure the bed surface is clean and the first layer is well-adhered before starting a long print.
Verify stepper driver current settings.

If the printer uses adjustable stepper drivers, check that X and Y driver current (VREF) is set correctly for the installed motors. Too low a current causes step loss under the load of axis moves. For Prusa printers with TMC drivers, the values are set in firmware and typically correct from factory — only adjust if other causes are ruled out.

When to Call a Professional

If all belts and rods are in good condition but shifting occurs consistently at the same layer height, a partial nozzle clog causing head collisions or a stepper driver failure may require further diagnosis.