"Disk Full" error message

I am using Duplicati to back up from one unraid server to another, and I got:
One or more errors occurred. (Object reference not set to an instance of an object (Object reference not set to an instance of an object) (One or more errors occurred. (Disk full. Path /backups/duplicati-…
I have 6TB of unused space in the target system.
The source system is, admittedly, receiving 2TB of files copied from another NAS box. The log data I have seems irrelevant:

  • 22 Nov 2019 03:22: put duplicati-b79dc4ee81a7d482394038b8f340957c8.dblock.zip.aes
  • 22 Nov 2019 03:22: put duplicati-bb17b3dd479d441cb84aeb27d2369985e.dblock.zip.aes
  • 22 Nov 2019 03:21: put duplicati-b7d35531757ad4755a44d01d96845f955.dblock.zip.aes
  • 22 Nov 2019 03:21: put duplicati-b78b5fa2bc81c4db69f93ec2cc6e535ba.dblock.zip.aes
  • 22 Nov 2019 03:21: put duplicati-b5d6c297c94c54a92a9e94b2276c7b99f.dblock.zip.aes

Welcome, @ahowlett. Hope you don’t mind but I moved your post to a new topic since it was not relevant to the Google Drive thread where originally posted.

In any case, couple questions: Are you running Duplicati directly on each unraid system? Can you confirm the free space on the system where you received the error? (Sounds like you already checked free space on the target…)