Curious phenomenon when printing a vertical Whitworth thread

Bambu Lab X1 Series Bambu Lab X1C
1

Lately, the upper flank of the thread is missing when I print it in a vertical orientation. Strangely enough, other curves and overhangs on the same object – including the lower flank of the thread – are printed perfectly fine. The issue occurs regardless of the filament used.

Whitworth thread failure
Whitworth thread failure409×552 134 KB

Any ideas what might be causing this?

2

Are you printing TPU here?

3

No, in this case it was ABS, the same with PETG HF.

4

Slicing seems fine, assuming you have minimally 2 walls.
What is the nozzle diameter, bead width and layer height?
Too hot could give the opposite effect, but this is weird behaviour.

Maybe some others have a thought.

5

Settings
Settings562×587 24.2 KB