1st things first, ensure your Snaps are using the latest s/w I'm using version 3.4.790 and have had no probs, other than slowness because I can't load a Veritas Agent on to them.
A workaround is to have a bucket load of space on a server and use robocopy (see NT reskit) to copy (with a /mir switch) from a specific share on the snap, to a specific folder/share on the server. Load the agent on this server and back it up to tape.
That way you have an instant retrieval (from the server copy) in case on of the users 'accidentally' deletes something, and an offsite copy on your tape!