[BUG] MK4S default [email protected] first layer too high

[EEJoshua]

Printer model

MK4S

Firmware version

6.1.4+7908

Upgrades and modifications

E3D 0.6mm High Flow Brass Nozzle, Satin sheet

Printing from...

USB Drive/PrusaLink

Describe the bug

When printing with Generic [email protected] profile in PrusaSlicer 2.8.1, the first layer is too high and causes bad or no adhesion.
Manually adjusting live Z height by ~-0.1mm fixes the issue, or setting the filament type to PLA in slicer settings also fixes it.
Not sure if happens with 0.4mm nozzle

Longer explanation:
I noticed all PETG prints have too high first layer and cause it to fail almost every time.
PLA prints perfectly every time.
After some experiments I concluded it happens when printer "thinks" it's printing with PETG vs PLA.
I use "Generic PETG @MK4s HF0.6" with default settings, I suspected there is a bug in printer firmware so I tried slicing the same with just one setting changed: Filaments -> Advanced -> Filament type -> PLA.
This ensures all print settings are the same, just the printer thinks it's PLA.
This change solves the problem completely and the first layer is perfect as it is with actual PLA.

I contacted Prusa support, they said the only difference this change causes is that the mesh bed leveling happens at 175C for PETG and 170 for PLA, so I tried reprinting both files, but setting the mesh leveling temperature manually to 170C for PETG file and 175 for PLA file, and again it fails only for the file it thinks is PETG, regardless of the mesh leveling temperature.
In the attached image you can see the first layer with each combination:

1. Default - Default PETG profile with default settings and default mesh leveling temp (175C for PETG)
2. "PLA" - Default PETG profile with PLA filament type setting and fefault mesh leveling temp (170C for PLA)
3. Default+170C - Default PETG profile with default settings and manually changed mesh leveling temp (170C like with PLA)
4. "PLA"+175C - Default PETG profile with PLA filament type setting and manually changed mesh leveling temp (175C like with PETG)

It is clear that the problem persists with the PETG filament type.
I attached the sliced files, I don't think there's anything there since they're the same except for the filament type.

How to reproduce

Print anything with Generic [email protected] default profile

Expected behavior

First layer should not be too high and the print should stick to the bed.

Files

Keychain_gcodes.zip

[fdkuiper]

Just to confirm: I have exactly the same issue on the same printer with the same nozzle. Really annoying!