Hi! There are many factors as to why your layers are shifting. Consider inspecting these checklist to find out the problem:Misaligned belts - you can check this video to fix your belts.Improperly calibrated trimpot - It can be that your current set is too high or low.Bad rod - if this happens you need to replace your rail.
Stepper Drivers - Check the current settings of your stepper driver if it's too low/high, it has missing steps or going into thermal protection.