Need to access (without installing client) NW 6.5.8 server from Server 2012 R2.

Up to Server 2008 R2 Domain authentication works perfectly fine, on 2012 R2 I managed to get it working a couple of times, never again. Reverting to eDir authentication with SMB Signature disabled works (can access shares fine)

Is that known issue? (not that I would expect any fix for an obsolete OS)