I have a similar but different issue with my Windows machine. To backup my computer I use Veeam Agent. I also use the UnRAID box as a NAS, so I have a share mapped in Windows Explorer to access my files. The issue is that Veeam gets a "Failed to create or open file error" if I try to login with the same credentials I use to access the NAS from Windows Explorer. The way around this issue is to make a separate account on UnRAID and use that with Veeam, but of course that's not optimal. Any idea how to fix this?