Weird behaviour : z probe offset bed levelling

Hi,

I tried everything to solve my problem and I can't find an answer anywhere so I am giving it a shot here. Sorry if it has already been answered.
Everytime I do an automatic be levelling (any type) my z offset is going to be off by 0.05mm. Even when I tune it in marlin (add the difference to the z probe offset), I still need to add another 0.05mm using the lcd or it will print too high. Let's say the software is set for -1.25mm, if I don't adjust I manually to -1.30mm it will print 0.05mm too high. However if I modify the software to get a -1.30mm offset, I will have to manually set it to -1.35 for the first layer to be the proper height. I onky need to do it once every time I power on my printer and not after every print.

Does anyone have any clue about what is happening?

I have a similar problem, after G29 the height of the Z axis changes. I changed the start script:
G28
G29
G0 X0 Y0
G29
After executing this script, the height of the Z axis becomes normal, without any additional changes.

Full description of the problem [github.com]

Edited 1 time(s). Last edit at 10/08/2019 03:17AM by komandr.