First layer lifting after few days

Chels

Hey everyone!
I am rather new to the Repetier Server. My pulse xe and my prusa are connected to it and it worked great (aside from a small issue that got fixed with an update).
But now I am quite baffled and confused.

For around 2 weeks both printers start having first-layer issues. It happens every few days that the print fails and when I start again to see what is wrong I see that the first layer prints too high up. But just by enough to lay down the first layer to disconnect the print just a bit in.
When I recalibrate the Z offset (on printer for prusa, per mattercontrol with pulse) it seems like it is actually the same offset as before, but it prints again a perfect first layer.
When I then reconnect the Printers to the Server it works like a charm until a few days pass and the print fails again because of a too high first layer.

First I thought that it is an issue with the printer, but it wouldn't make sense that both printers have the same issue at the same time.
Also that the Z offset seems to be the same as before is weird to me.

Hope one of you can help me or guide me to find out what it is!
Thank you very much~

Repetier

Of course we do not send a secret command to misconfigure printers after 2 weeks:-)
But sounds in deed strange. We have no control over Z positions/calibration. That is a printer internal setting stored in their eeprom I hope, or resetting/disabling printer would loose them. What might have happened is that you send somehow
M502
M500

to reset eeprom to factory defaults. Did you maybe use our eeprom editor and used that function? Otherwise I have no real idea apart from explicitly changing that setting with the proper M-Code.

Chels

And no secret commands for printing small cats to cheer people up? :O now I am disappointed :D

I thought that maybe something about the z-height could be misconfigured so that it doesn't run along the whole rod, but it is also testing the bed every time a print starts.
No M-Command has been touched! I slice the stl through mattercontol/prusaslicer and just upload it to the Server to print.
Can't make sense of this, through the only common thing between those two printers is the Repetier server... or gnomes that sneak out at night to turn each rod by one click :o

Repetier

The G28 W for prusa makes it autolevel every time, that is correct. But also note that this uses the z offset stored in printer firmware. So note that value and if it fails again compare with old. If it is the same it should stick as before (does for my prusa). If it changed ok it would not stick depending on value. But I never had it change so far on my printer. Actually don't even know if it can be done outside lcd menu.