having 4 full log files generated within 2 minutes of each other would mean either some debugging is turned on way too high or there are some serious errors that are causing the log to fill up very fast. It may be a good idea to contact support for someone to look at the configuration and make sure there is nothing wrong.
the CVD log on the media agent side also does not seem to have any particular error in it, just a clean shutdown of the pipeline after the tape has been mounted.
it may be easier to escalate the issue with someone in support so they can get the picture of the whole environment to check the necessary logs instead of trying to go piece by piece here.
On a side note, when did this issue start happening ? Were jobs running for a period of time and then this issue started happening ? If this is the case, what has changed on the setup between succesful jobs and this failed job. Were updates installed, was some software upgraded ?
Are there other subclients which are successful, or are all subclients failing with similar errors.
Wearer of Many Hats