I ran auto level, saved, and then I manually adjusted each corner. My g-code calls out M420 S1 so it's supposed to be using the mesh.Are you saving the settings after leveling? The system should reboot after setting the Z offset.
Are you doing an auto bed leveling before every print? Some people do a manual level and one auto level then don't allow it before every print.
Some people only use a manual level and shut off ABL.
Definitely sounds like there is an issue but being 1600mi away it's hard to diagnose.
I'm not sure if possibly something is loose or if there is a software issue.
It's one corner that keeps losing level but it's not loosening and raising, it's actually dropping.
I have the official Creality Ender 3 Max enclosure but it's just too small it seems like, and it appears as if the right front leveling knob was catching on it. I had to adjust it some more but it seems to be back level again for now. Printing again so I'll know here within an hour or so. If this one prints successfully I only need 9 more by Sunday.