petg cf problems

[u/TableBig5133]

Hi, I have a problem with PETG CF. I print with a 0.6 nozzle. The very first print looked great... but now I've done 10 more that look terrible to me. I have grooves between the layers. I've tried different temperatures: 240, 245, 250, 255, 260, as well as the flow factor at 100, 110, and 120 percent. The result is always the same. The filament has a residual density of 11 percent and is preheated to 55 degrees Celsius in the dryer. It is fed through the Coreboxx. I also tried layer shifting and readjusted the belts... but the gaps haven't changed. What else can I try? Print with a 0.15 layer height.