Hotend/heat sink slipping downward.
I have an i3 Mk3S with a total of over 63 days of relatively trouble-free use accumulated so far.
A couple of months ago I found that the nozzle of my printer had dug into the steel sheet during the early stages of a print, resulting in permanent damage to the sheet. It turned out that the whole hotend/heat sink assembly had slipped downward slightly and increased the nozzle-PINDA sensor offset by a millimetre or so. I disassembled the extruder enough to reposition the heat sink and retightened everything. After re-calibration, all worked well again.
Today the same thing happened a second time. I have repositioned the hotend assembly and recalibrated once more and although all is working well at the moment I am concerned that the fix is not permanent.
Is there a simple solution to this issue or is it necessary to replace some parts in order to prevent it happening in future? If so, which parts?