It is recommended to run a FSR (File System Repair) to check your system if there is a write failed issues, and you can do that by following the steps in this link:
http://kb.open-e.com/File-system-repair_138.html

And did this just happened now and it was working fine in the past, that means you could have a hardware issue, and it is recommended to check your hardware if there is any issue or not.

Also the NAS-XSR has EOL (End OF Life ) from a long time ago, that’s why we do not have support for it right now, and you can find EOL for NAS-XSR at this link:
http://www.open-e.com/service-and-su...ducts-archive/