How come the 1752_579012765.xml file is not there?
My guess is it's bogus. Whatever made CBS think that it should exist is part of your corruption.
FWIW all of my current sessions start with 304 too.
Otherwise the only thing that I imagine may be possible is looking at the Sessions instances, guessing that they are constructed from the individual files, so then if both Sessions instances each contain 1 more "session" than you have of the individual
304 variety perhaps you could make your own out of the excess. <eg>
BTW what is a "back" anyway? E.g. if it is just a backup copy of the preceding session that would cut your work in half. In fact, it looks like there is some size relation between them but we would have to open some up to see why.
Good luck