Downgrading samba packages to version 2:4.1.17+dfsg-2+deb8u2 (stock Jessie version) plus downgrading some required libs (also to stock Jessie versions) solved the issue for me:
> sudo apt-get install samba-common=2:4.1.17+dfsg-2+deb8u2 > samba-common-bin=2:4.1.17+dfsg-2+deb8u2 > samba-libs=2:4.1.17+dfsg-2+deb8u2 python-samba=2:4.1.17+dfsg-2+deb8u2 > libsmbclient=2:4.1.17+dfsg-2+deb8u2 > libldb1=2:1.1.17-2+deb8u1 python-ldb=2:1.1.17-2+deb8u1 So it's clearly a regression which had been added, unfortunately, by a security update for samba. I also forgot to mention that this issue breaks connection to smb shares for various file managers, including Caja and Krusader. It's not possible to connect via them, they show an error message dialog instead.
