Z axis changes on its self?

When i put the right coordinates for the tools on one day and evryting is working fine.
A day later when i send the bod to the same z coordinate it stops higher, it can be 0,5 cm till 1 cm.
Did anyone has this problem and how can i fix it?

Are you using encoders? Using Find home more often or enabling Use encoders for positioning may help.

Done both