I'll send you v0.8 maybe that makes things a bit better.

Otherwise: Its always happening with GND FBM or its specific to this cloth?

It might relate to the settings used or the version fails to collect the active GND targets to recognize they belong together.

If you increase the value in the "do not move vertices..." that things that defaults to 0.02, does it get more "consistent"? Either consistently good or bad. The hard break might indicate that vertices nearer than 0.02 are being projected and vertices > 0.02 are being ignored. The distortion horizon could be vertices near 0.02

Skirts are catastrophy anyways :)