Sorry but this is user error.
Bundles are for backward compatability and date back to a time when file compression wasn't a standard Wimdows function.
Not recommended.
If you insist on using bundle files then:
The appropriate workflow is to create a cwp file, then it will save as a background process. When you're finished your project and want to archive it then save as a .cwb.
The way you're using it, or wanting to use it, you have to invoke the compression algorithm every time you save.