I changed my PEI sheet, as I’ve done a few times with my (year and a half or so old) Mini. I took the opportunity to tighten the screws under the heat bed and clean all that off with some rubbing alcohol. After changing the sheet I reinstalled the build plate, put the probing discs back in, tightened them down, reconnected the two connectors that go to the heat bed, and turned it on.
Now whenever I try to start a print, the nozzle mashes into the first probing disc it goes to (to the point that the stepper starts skipping and I have to turn it off). I’ve tried taking the screws out and putting them back in, cleaning off the discs, cleaning off the nozzle by hand while it’s heated up, checking continuity between the probing disc and the wire that is bolted to the aluminum plate (continuity is fine - the nozzle should sense the disc as far as I can tell). Nothing seems to fix it. What have I done?!