All the relevant servers are running Server 2012. We do straight backups to tape. Our backups are traditional Full on Friday to LTO8, Incremental on other weekdays to LTO7, on an external LTO8 ad LTO7 drive respectively. These are direct backups to tape, not backup to disk first. The backup server is a physical machine; the ones being backed up are VMs on a separate Svr 2012 Hyper-V server.
The Full job runs successfully. The Incremental jobs, however, complete or almost complete, but the last one sits there at Active: Running when we come in in the morning. There is no backup activity going on: the light on the drive is solid, not flashing. It just sits there until I cancel the job.
The backups have been running successfully for years, but started pulling this nonsense about a month ago. We haven't made any big changes on the network. The backup selections look good as far as I can tell, and NTFS permissions on the folders to be backed up seem to be fine.
I have tried using different Compression methods, without success. I've tried running the Incremental job on a different tape drive, but the issue then occurs on the other drive.