Z-height issue in rear left corner (solved!)
Searched google/the forum and couldn't find anything related to this, so figured I'd share in case someone else is having a similar issue.
I installed the nyloc mod on my MK3S+ today and got my leveling dialed in to o.o1 via the Prusa Leveling Guide in OctoPrint.
However, when I went to print the Bed Level Correction file to confirm my settings, I kept getting a really shallow spot in the back left corner - to the point where I actually scratched my bed after live-adjusting my z-height compensation during the print. 95% of the bed was perfect - but this one spot was driving me up a wall, and didn't make any sense.
I took a few minutes to manually move the bed/gantry around at Z+1 to watch for any inconsistencies, and wound up noticing that the bed would bump up by approx +.75 or so in the back left corner (right around where I was having the issue). First, I thought my bed rails might need adjusting.. so I inspected further while stepping the Y-axis back and forth over the bump. Didn't take long for me to realize that one of my temperature sensor wires under the bed wasn't properly secured, and was pinching between the underside of the bed and the gantry frame, causing the bed to shift upwards when it would cross that spot on the Y-axis. I tucked the wire away, and boom.. problem solved.
Out of all the possible causes, I didn't even consider a stray wire... so, yeah. Hopefully this can help someone else out there.