Backup jobs fail due to ERROR CHUNK_MAKER Failed to read 0 bytes (Insufficient system resources))

The last line of the log shows:
2020-10-25 03:53:16.770 ERROR CHUNK_MAKER Failed to read 0 bytes: read \?\U:\DIRECTORY\TO\FILE\SOME_FILE.mp4: Insufficient system resources exist to complete the requested service.

Is the \?\U: pattern normal? Full path isn’t shown anywhere else in the log so I don’t know if this is simply due to inner working of Duplicacy or not.

Restarting the backup job goes through this file but fails with the same error on another file.

I use the Web UI
options: -threads 12
Global opts: -v
Files are in a Cryptomator Vault on an externad SSD. Vault is mounted and all the files are accessible. None of these files are open.

Any clue about actual the cause? CPU, RAM, Disk I/O are all OK and the file is readable shortly after the error that causes the backup job to abort.

I - personally - haven’t had a good experience with Cryptomator. In the future I will re-evaluate it.

One of the problems I had was precisely the high use of resources in some situations. Perhaps this is the cause of your problem.