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Hello everyone!

Veeam 12.3.2.3617, Community Edition, Workstation Backup by veeam agent

I’m having an issue with one of my home PCs. When I try to back it up, an error appears.

29.09.2025 21:31:17 :: Error: Unable to resend traffic block '15863' because traffic history doesn't contain this block. History low block id '15869'.
Failed to upload disk. Skipped arguments: [EmulatedDiskSpec>];
Agent failed to process method {DataTransfer.SyncDisk}.
Exception from server: There is no traffic block '15863' on the source side.
Unable to retrieve next block transmission command. Number of already processed blocks: [25496].
Failed to download disk 'bdd448f6-e7b0-4f2b-93b3-6eb675ad51c3'  
 

Backups of two other PCs to the same storage complete without any problems. What could be causing this behavior?

I tried replacing the target HDD — it didn’t help; the error can also appear when backing up the SSD (the drive’s health is normal, no errors).
I tried different backup types (volume, file-level, entire PC) — that didn’t help either.
I tried recreating the backup job  — no change.

 

Hi I found various Articles that stated to either check if there is an issue with not enough ram and others where the solution was to create a new full Backup. 

Have you tried to create a new full Backup?

Regards

Chalid

Hi I found various Articles that stated to either check if there is an issue with not enough ram and others where the solution was to create a new full Backup. 

Have you tried to create a new full Backup?

Regards

Chalid

Hi,

Yes, I found them too and assigned 12 Gb(6.5 was used) of RAM and tried to create Full Backup - no changes

Hm Ok. Have you tried to create a new backup Chain by choosing another repository or creating another job?

What you can always do is create a support request with veeam. They offer it for the community edition as well but only as best effort without any SLA´s. So it might take some time for them to answer.

Regards

Chalid

 

 

Did you check the logs to see if they indicate something to help otherwise support would be the last thing.

Logs - C:\ProgramData\Veeam\Backup\Jobname

Hmm...sounds like you tried about everything we could suggest ​@PavelD . About the only other thing to suggest outside of Support as Chris mentioned, is to make sure Antivirus tools aren’t hindering the process. Go through the following KB and verify all is good there:

https://www.veeam.com/kb1999

...if so, then I think Support is your best bet (yes, even with “free” edition; it’s a best-effort thing).

Best.

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