Welcome Djed.
Hmmm, my old PRT alpha goes "clunk" when I am zeroing it, so that may not be an issue for you. But your 2nd point sounds like a problem. My proximity switches always save me from hitting the end stops. But I am too light-weight of a user to tell you what is wrong.
But posting as you have, should be able to get some attention,,,,, though I would suggest a more detailed headline may be of help........... Newb with questions could be anything. And often such queries are superfluous. A headline like "Possible proximity switch problem" may help get someone's attention. And you can search for old posts that ask about proximity switch problems.
Good luck, Chuck
Chuck Keysor (circa 1956)
PRT Alpha 60" x 144" (circa 2004)
Columbo 5HP spindle
Aspire 9.0, Rhino 5