Windows Server 2012 R2 Backup "Incorrect Function" error

We have a customer who's running an older Windows 2012 server with an IO Safe and a nightly backup with Windows Server Backup.

This backup has been running in this configuration for a while with little issue, but sometime in the last few months it's started "completing with errors". On further investigation the backup is actually failing completely on the C: volume as well as the bare metal recovery with the error "incorrect function"

We've done a few troubleshooting steps at this point, we've ran chkdsk /r on the affected server with no found errors and no luck. We've tried to run the backup to our own drive and it fails in the exact same manner.

If I try to dig into the error any further I'm only able to find completely generic error codes and absolutely nothing that would point me in any particular direction. I'm somewhat led to believe one of the server's drive's may be failing due to age, but chkdsk didn't seem to find anything that would indicate so.

If anyone has any idea's on what we could do as the next step that'd be great. I know this setup is far from ideal but right now we'd just like to get a successful backup done so we can know they're covered in the event of a hardware failure. Thank you!

Edit: I also just checked the drive's self diagnostics and they're both reported as healthy. That's for the source and the destination.