STRANGE X-Y JUMPS

[Erik_Es 1]

If your printer is suddenly making strange x-y jumps that are causing misalignment of the layers, the problem is USUALLY either very loose belts or one or more loose pulleys that need tightening.

BUT there is something else that can cause this (at least with Ultimaker Original, don't know about UM2):

if the cooling fan on the motherboard is not functioning properly (or not at all) then some parts on the motherboard get overheated which causes extremely nasty jumps (accompanied by horrible banging sounds).

Solution: turn off the printer and either replace the fan if it is broken, or if it is dirty and/or running too slow or irregularly, then clean out all the dust and push some bearing grease in the hole under the round sticker. Before reassembling, connect the fan to the motherboard and switch on the printer (not too long, as there's no cooling on the board now) to check that is running and blowing smoothly.

It also helps to switch it on shortly while you put the grease in, that way the fan sucks the grease inside a bit more.