I'was trying to print a grid inside a circle.
With 4.0 I stopped the print right after it starts.
Because at the crossing section of the grid and the circle are lots of mini gaps and SD3 was trying to fill this mini gaps.
Drip by drip. Very slow! I mean, SLOW! You can't even see any action.
After I switched to S3D 3.1.1 to print, it runs perfect like every time in the past.
In that case the mini gaps don't bother me.
(Yes, it is partly the fault of my design. But I don't want to pay attention at the designing process, because of the slicer. And with S3D 3.1.1 it works like expected.)
I guess, it's a great feature, if you can switch it on or off.
I'm pleased for every hint.
It seems I do have that problem only when I use Extruder No. 2
So it's a different problem. Nothing to do withe the Gap-Fill.