Backupcopy fails unexpectally

[Paulo Balau]

We are backupcopying regular backups from a QNAP NAS to external USB disks attached to this NAS.
Weekly we swap the disks in order to have offline/offsite backup copies.
After updating to 9.5 Update 4a we start having this strange error and behaviour.

After a while (no pattern detected), backup copy fails (see error below).
I try to "sync now" and it resumes. Sometimes it finishes ok, sometimes fails again. And there is no size or time patterns I could detect!
I end up having several .vib and if reaching the number of restore points, on top of that, he starts doing merges.
Yes, on such events, similar error occurs also failing the merge process with similar error.
And I get stuck.

Example & Comments:
>> BackupCopy:
"Message: 14/04/2019 16:30:22 :: Error: An unexpected network error occurred.
Failed to read data from the file [\nasbak01\USB-BackupCopy-Week2\W2-BckCp-FileServer_QNAP-USB\W2-BckCp-FileServer_QNAP-USBD2019-04-14T000000_9608.vbk].
Failed to restore file from local backup. VFS link: [summary.xml]. Target file: [MemFs://frontend::CDataTransferCommandSet::RestoreText_{e7b1ff5c-b4d2-4754-9007-3f07cbc9c66b}]. CHMOD mask: [120].
Agent failed to process method {DataTransfer.RestoreText}."

It seems veeam tries to read from target, where is supposed to write!
Accounts are ok. Permissions too. If not we should get an error from start.
On occasion I've also forced to backup from one single repository (the QNAP) - no success.

Any help is welcomed!

[wishr]

Hi Paulo,

Did you have a chance to raise a support request? If not, this is a way to go since advanced troubleshooting involving debug logs analysis is required. Please, don't forget to reference your case ID here.

Thanks

[Paulo Balau]

ID Case: 03620809

[wishr]

Dear Paulo,

Thank you for mentioning your case ID!

Could you please upload your logs, as requested by our engineer, so we'll be able to try to catch up the root cause ASAP?

[Paulo Balau]

It was a simple DNS problem.
Awkwardly, backup server resolved the name of the NAS despite no entry on DNS
From time to time it didn't.After placing dns entry experienced no more problems