I am amassing my fleet of Benchy's trying to troubleshoot my printer. Of the last 7 (soon to be 8) only one large issue sometimes occurs, there is a shift along the x-axis (+) that, when it happens, always occurs at a 31mm height. This happens for about 2/3 prints. I'm kinda stumped, as by this time the printer bed has cycled through that area 100+ times so I wouldn't think it would be a belt issue or I would expect it to occur more "randomly". I thought maybe it was an issue with the stepper driver current, but it happens at the same height on both 0.2mm and 0.12mm layer thickness prints. My (potentially faulty) logic was that if it was a current issue it should show after a given amount of movement, so lower on the 0.12mm. I've checked all the belts, grub screws, etc. Any ideas?
I'm having (had?) the same issue in Ydirection. It seems that the friction of the gantry was too extreme. After not being able to get the right tension to fix this I applied a bit of lubricant fluid to the "wheels" and since then it moves without skipping steps (which was the main reason I think!)
Layer skipping at the same point in both models is likely always related to gcode issues when copying over from your PC. Things to try would be formatting the SD card to a lower volume (500mb) and using a different reader/writer/pc when copying the gcode.