The initial errors
[90:182] Cannot forward segment.
[90:65] _*****:
Cannot append to medium
are coming from the Backup Media Agent (BMA), and, unless the Open VMS system is also acting as teh Media Agent for this backup, I think that this is most likely going to either be a hardware problem or bad media
Do a Verify on the Media using a different drive than was used for the backup, depending on the type of media, this can take 2-4 hours. If it is successful, try using the media for a backup again, if it fails, the media my need to be discarded
If this drive is failing consistently, it is probably bad, and will need to be replaced