Could not find file, 403

I keep getting this error, its a large backup around 2TB.

One or more errors occurred. (Could not find file “/tmp/dup-a3a2cd11-f467-4a2e-8b68-a5d960a26b4b” (Could not find file “/tmp/dup-a3a2cd11-f467-4a2e-8b68-a5d960a26b4b”) (One or more errors occurred. (The remote server returned an error: (403) Forbidden.)))

Does anyone know how to fix this?

What backend are you using?