I also had the problem of the filament sensor now. I opened the module and removed the switch. The reason for me was that the upper part of the switch was not firmly connected to the screwed lower part. In addition, the mounting screws were not tightened enough.
That’s why the Cu release contact sheet was wedged inside (perhaps due to vibration or something else). I fixed this and fixed the upper part with the lower part with a drop of glue. Then after the check (click and press the spring) reinstalled and tightened the screws.
Caution : when dismantling the switch, a small white plastic part which keeps the release spring tensioned is inserted loosely - do not lose it !!!
The filament switch works perfectly again.
If a Snapmaker ADMIN is reading along:
Would it be possible to announce the type of this switch?
In the trade it would probably be easy to get and exchange.
Greetings Wolf from Austria