I have the same problem as @x86 with the NAS on a fritzbox 7560. Fritzbox 7560 is a box with USB ports to attach hard drives, that I can then mount in Win 7.
The problem started when the fritzbox updated its OS to FRITZ!OS 07.27
I believe the error message is related to the SMB version of the SMB server in the fritzbox, because I also got problems with a Win XP machine not being able to access the NAS. I ticked in the box settings:
‘Activate support for SMBv1’ and the XP machine could access the NAS.
Duplicati starts as a task with elevated rights when I log on to Win 7, so I think Duplicati has access to the network share, at least there were no warnings prior to the box OS update. Yet when I back up the network share Z:, I get many instances of
2021-06-12 23:26:42 +02 - [Warning-Duplicati.Library.Main.Operation.Backup.MetadataGenerator.Metadata-MetadataProcessFailed]: Failed to process metadata for “Z:\lisezmoi.txt”, storing empty metadata.
I took the following measures: disconnect the network share, reconnect it.
Your thoughts on this topic?
JF
Duplicati - 2.0.6.0_experimental_2021-04-09
Windows 7 Pro version 6.1 (build 7601)
FRITZ!OS: 07.27, SMBv1 active