In the last couple of weeks, it started showing slight layer shifting on random layer heights on all models I tried to print with multiple different slicer settings, and with all the filaments I have tried (PLA basic and matte, PETG, and TPU for AMS, all BL originals using the BL studio original profiles). The filaments are kept dried inside the AMS with a hygrometer displaying between 10% and 18% every time I check.
After a bit of reading, it seemed the issue could be loose time belts, so I performed carbon rod cleaning and belt tensioning, according to the BL guide video, run a full calibration, and printed a calibration cube (MakerWorld model - 0.2mm layer, 2 walls, 15% infill) on BL PLA matte using the original BL studio material settings, and also printed the 3D benchy straight from the printer on BL PETG, and the issue is not resolved.
Have you cleaned all of the idler (smooth) pulleys? Mine accumulate a black crud on them that I remove with a q-tip and alcohol. Sometimes I use an old toothbrush to clean the grooves of the timed belt pulleys. It may help.
After battling with it for about a week, trying anything I could think of, and having inconsistent results, I realised I was an idiot…
The inconsistent layer shifting was a direct result of forgetting to screw in the screws that hold the hot end in place when I switched hot ends. I screwed them in and tightened them and I have been having quality prints since then.
I was so embarrassed and thinking of deleting the thread, but I will leave it here for posterity.
This happened to my old Prusa MK2 machine. The fix for that was to disassemble the axis and give them all a thorough clean and reccommended lubrications and machine oil.
The jumps you are seeing is usually caused by a sticky X axis, expecially with it getting worse with time. Once it jumps at one point, it makes that spot worse. Think of it like a flat spotted tyre in formula one, every lock up afterwartds is going to the same flat spot and make it worse.
