Roger -

You may want to experiment with COMPRESSAlways=No on some of your
more "interesting" clients.  It can impact client backup performance
where a whole transaction has to be re-done, but will save you from
the server issues you're encountering.

To deal with the individual problem files in the stgpool, you might
try using Virtualnodename (if available for the platform type) to
restore the problem file to a like system and then back it up again
without compression or COMPRESSAlways=No.  A Deleted Backup or EXPire
command at the proxy client may be suitable to clear the thing from
the stgpool.

   Richard Sims