Hello,
I use Opus v12.19 here and have the issue that my freenas network drives log mounting errors on the server because opus is trying to "mount" networkshare:OpusMetaInformation as a path which does not exist.
Is there any way to prevent DOpus from using the metadata saving technique (NTFS ADS) for network drives?
Not without disabling it entirely.
But other software will still try to use NTFS ADS in places, so that still wouldn't really solve things.
I would be asking the FreeNAS team how to stop their software logging errors for completely normal requests to the protocol they only half-implement. 
Thanks, maybe it is missing something in my freenas config. The volumes serverside are ZFS, but for some reason my windows detects it as NTFS. Will try tinkering a bit with the supported features, maybe ZFS has something similar like ADS.
/update: it should support NTFS ADS compatbility by default, so my best guess is that the CIFS Server seems to try to open a path with a colon inside of it which is invalid for windows clients but not for Unix systems. I noticed it only throws errors on the root directory of the share, not the subfolders and files. I am gonna go ahead and post a bug report on the freenas bugtracker for this. Thanks for the quick answer.