Backup failed with permission error and Errno is 0

We are having some trouble with backups failing with the following error

Errors - 05/07/19 21:07 - Error while getting files in folder “/opt/xxx/xxx”. User may not have permissions to access this folder. Errno is 0
Errors - 05/07/19 21:07 - Indexing files failed, because of error
Errors - 05/07/19 21:07 - Constructing of filelist of “server1” failed: error - index error
Errors - 05/07/19 21:07 - Backup had an early error. Deleting partial backup.

It seems to be that one of the files in that folder have wrong permissions (0000) but would it be possible for the urbackup client to just skip those files. We have checked the setting “Do not fail backups in case of hash mismatches or read errors” on the server but without any change.

Server OS: Ubuntu 16.04
Urbackup server version: 2.3.8
Client OS: Ubuntu 16.04
Urbackup client version: 2.3.4


I am getting the same error on Debian Server 2.4.13 and a Linux client.

Any recommendation?