Snapmaker A350T, PETG, pillowing and horizontal errors

Hello snapmaker friends,
I have some problems I can’t get rid off.
Maybe you can help me.
As you can see I have a problem with, it looks like missing material at some points.

I have tryed to slightly increase my flowrate by 0.01% steps up to 100.07%. It didn’t help.
On this second picture you can see that I don’t have the problem on this part of the print.

For the pillowing on the top surface I already found some advice here on the forum, that I will try with my next print (increase infill percentage and number of top layers).
For the print I have pillowing with I have used 15% tri-hexagonal. I will try it with 20% cubic.

What I also found is some missing material on the initial layers, as you can see on the 3ed picture. It looks like it happens only near corners.

I have printed ASA, TPU and PLA with nice outcome so far, but I can’t solve my problems PETG.
My settings are:

Layer height 0.15
Layer width 0.4 with 0.4 nozzle

Infill 55
Outer wall 27
Inner wall 55
Overhanging wall 20%
Top/bottom 27. 5
Travel 70

Top thickness 1.5mm
Layers 10

Print temp 234
Bed 90
Fan 40%
Retract 3mm
Speed 45mm

Material Verbatim PETG 1.75

Thanks in advance for any advice

PS: I can only add one foto to the topic since I’m a new user. I will add them with further postings

Here is the second foto

And here is the bottom

Thank you

Make sure you have done your e-steps, retraction, and flow calibrations. Then check that your slicing software has the “Combing Mode” setting set to “Within Infill,” and reduce your print speeds (no more than 40mm/s). These will fix 99% of the problems with PETG printing.

Thanks for your advice. I have done the e steps calibration. Combing is within infill. Is it not possible to print at “higher” speeds with good results?

Sometimes, but PETG generally needs slower speeds than PLA in order for it to have time to lay down and adhere properly. It also needs less cooling…set initial layer fan speed to 0%, and regular fan speed to 40% or less.

Is it correct that PETG should be printed with a wider line width than the nozzle size? On reddit somebody adviced me to use 0.45 with my 0.40 nozzle

I have never heard that nor done it. For all types of filament that I have used (50% of my prints have been in PETG), I have always set line width to be exactly the same as the nozzle diameter. It could depend on the slicing software you are using though; I do know that Cura/Luban (I use Cura) and Prusa/SuperSlicer use very different algorithms for calculating line width, so perhaps that extra is needed for PS/SS.

I have done some new test prints.
Here is my outcome. Most of the outer walls are looking perfect, but at some spots I have this strange errors. I have no idea what is causing them. The seam is on another position as you can see on the second picture.
Any ideas?

Thank you!

playing the replay I recognized that it might be after the start at the seam. what is strange is, that it doesnt happen after every seam even though the failed layer is in the print direction after the seam. I dont understand why it doesnt happen after every seam.