thanks for the hint.
Yes, the folder is exactly the same and hence also does have the same permissions. I’ve doublechecked with ls -la
However adding the version (nfs only supports vers=2,3,4 according to https://www.systutorials.com/docs/linux/man/5-nfs/) did not make any difference.
Since it is working with CIFS, i think I’ll leave it like this.
However if anybody knows what could be the reason just inform me.