On the subject of the backup failure...
IMHO (and experience but YMMV), it's a complete waste of time to backup a 2TB log file (happened to me the 2nd day of my current employment but was only 250GB).
Take another full backup, set the recovery model to SIMPLE, do a CHECKPOINT or two, set the database back to the FULL recovery model, and take a DIF backup (or another FULL, if you prefer) to restart the logfile chain.
Then, make sure you get alerts if the logfile backup fails in the future.
As a bit of a sidebar, I'd look into my index maintenance routine and eliminate the use of REORGANIZE. It's not the "lower resource, log file friendly" tool that people say it is. Like I tell and have proven to people, "It's better to do no index maintenance than it is to do it wrong... And, if you're generically using REORGANIZE, you're doing it wrong".