first layer, oddly decreasing printquality

[simowaves]

Hello, recentrly i have been experiencing a rather dissappointing first layer, not beeing filled completly till the edges and having airgaps. So i ricalibrated z height and tighten the belts.
First print turned out great and then print after print it got worst again, what can it be? I used always the exact same gcode, and printed one after other. so must be printer, is it the belts? See pic
Thanks alot

[simowaves]

Update: i lowered/ricalibrated the Z height again and it did the trick
So quick question, after i set the new z zero height, i have to store it to EEPROM to have the settings after shutdown, is that correct?

[geneb]

When you set the new Z-zero point using the front panel, you're setting that change in EEPROM.

g.