Allocating a GID leads to a segfault, if winbindd has just started and is not fully set up.
Volker has a patch, already :-)
This bug was referenced in samba master:
Created attachment 16571 [details]
Patch for 4.14
I believe this is a 4.14 thing only
As Samba 4.14 is now discontinued, I guess this bug can be closed.