PLA Filament breaking

Hi,I have an unusual fault. One of my printers is a Tronxy XY100,with a PLA filament spool next to it,to feed it. I set up the printer,print off my parts,then wait for it to cool,then turn it off ,then cover the whole thing with a dust cloth,.About two days later Ill check under the dust cloth and the filament is snapped about 4 inches from the feedmotor,curled out backwards. It does this quite regularly,and Im at a loss to explain it.Bit of a pain to reheat the hotend to pull out the broken bit and rethread it everytime. Anybody with ideas?