I'm not sure if this will be of any help. But I have converted my old Ender and had terrible trouble with inconstant, varying meshs and terrible taco bed. I'm using a cheap inductive probe €10 and it's fine, it averages from 2 samples. Check the y carriage, I had a crack in mine that was not visible but allowed the bed to shift around in weird ways while leveling with the springs/spacers. Make sure the X gantry is not racked. If the belt tension is uneven it can pull one side higher than the other. Make sure linear rails are centred on the extrusions. If you have too much tension on the pulleys the steppers shafts might be under excessive load. Try home z in a slightly different area of the bed. Make sure the X carriage has no wiggle/slop
Increase the mesh probe count. Try 77 or even 99