We have a related issue: with VBR 188.8.131.523 with Tandberg T24 SAS Library:
The LTO Library appears to working well with tape jobs but sometime the "Tape Discovery Job" start nearly the "Tape Backup Job" and then both jobs stuck on 0% (discovery job at 0%, backup job at "starting new tape backup session").
If I try to manually stop the "discovery job" it remain on "stopping" state.
The only way that I find was to restart the backup server (all-in-one installation).
This happen frequently.