Sounds very similar to a failure I had on my HDZ, after upsetting it by losing steps on the way down it went into the Z limit switch hard enough to jam it on (closed circuit) permantly, this seems to be a common failure mode for these Omron switches, I’ve lost two that way and now keep a small stash of spare units. The Z homing failure on power up also sounds familiar.
I found RS components has the Omron equivalent for much cheaper than the DigiKey, but now RS lists all of the D2QW microswitches as discontinues.
You can use the D2QW-C003D or the D2QW-C003H only difference is this unit has pins for PCB through hole rather than solder tabs but checking the Omron docs this is the only difference.
Farnell has also dropped the C003D which suggests RS just ran out of old stock before the others did. They still have the C003H pin variety which I have used.
Mouser still has the D (but for how long?) and Digikey also has them.
When you get the replacement and solder it on use the Settings screen in Carbide Create to check that you’ve got it working, use a finger to operate the switch and check the Z comes up to show it’s active.