Hi there,
Could OMV Samba be updated to at least 4.8.4?
A confirmed bug exists when trying to delete non-empty directories for Ubuntu (Nautilus) or Linux Mint (Nemo) -
https://bugzilla.samba.org/show_bug.cgi?id=13204
The bug is described in this thread
https://lists.samba.org/archive/samba/2018-January/213048.html