interesting... not problem anyone else has reported.
Download/install our revised CB2025 setup file to get you to our newest build here: https://www.comicbase.com/mycb/Registrations.aspx
Re-launch the software, go into File Menu>Tools>Optimize. See if that helps the next time you try to save a compressed copy of your db.
*Also, check your hard drive isn't tight for space, free up if need be (empty your recycle bin can help too).