I'll try and explain what I mean.
tronxy X5, Marlin bugfix 2, but had same problem with 1.9
Bed auto levels, using BIQU level senor. Glass tronxy bed
Z homes to the middle of the bed.
3 x 3 grid.
rear 7.14-7.29-7.34
mid 7.76-7.74-7.78
front 7.26-7.50-7.07
Laying a steel rule confirm that the middle X is lower than the outsides.
Printing a test raft, the rear and front are thick, measure at 0.35mm. But the middle is very thin, measured .25mm.
Get the same results if not using a raft.
I would have expected the middle layers to be thicker, and the front/rear layers to be thinner.
