GFS has a failure mechanism to catch GFS periods missed due to job failures:
https://helpcenter.veeam.com/docs/backu ... ml?ver=110
>If there is a technical problem, for example, the tape library is offline, or the backup server is down, the GFS job will not run. When the problem is fixed, the GFS job will archive one most recent missed full backup for each media set.
The User Guide is a bit modest here, it will try for quite a few periods in fact.
In 99.9% of situations if there is a hardware issue during tape backup, as long as the server hosting the Configuration Database wasn't affected, at worst you'll just need to rescan the tape server and let the job run again, and it will handle it just fine

If the configuration database server was affected, I would still run the job and just see if errors appear, but there is a non-zero chance of potential database inconsistencies...but it's quite rare I would say as I just cannot recall any cases with such a scenario that had DB issues.
If there is a failure to the tape hardware, I would advise just out of caution to retire that tape (not a Veeam process, I mean just pull it out of rotation) cause who knows what might have happened to it when the drive suddenly just stopped mid-write.