Connect to a Samba share from a Windows 8 or Windows Server 2012 client. Right click on a file in the share, and select Properties->Security->Advanced->Effective Permissions

You should see a window that allows selection of a User/Group or Device. Click on "Select a user"and a standard domain search box comes up. Enter a valid user for the Samba share you're connected to and press Enter. If multiple names come up just select the most appropriate one. The button below the select User/Group labeled "View effective access" will be enabled (it was greyed out before selecting a user).

Click on that button ("View effective access"). You will see a yellow box that says, "Computing effective access" which after a few seconds will change to "Code: 0x80070057 The parameter is Incorrect." and no rights are displayed.

This only happens with UNC mappings; mapping a drive letter _works_fine_ and doesn't give an error ("NET USE * \\sharename\filename" for example, then perform the above the above steps on a file on that drive letter).

Initial troubleshooting using Wireshark indicates it negotiates the SMB 3.0 dialect, but the packet stream doesn't show any obvious candidates for what the problem is. Samba NEVER returns error code 0x80070057; the Windows client is generating that for an unknown reason.