I'll add a bit more to this as there is another issue causing me to loose work. I'm using R190 64bit of Windows 8.1 with the capx being stored in google drive.
Sometimes after autosaving saving fails to do anything. So if you press the save icon it doesn't become disabled to show that the capx is up to date. So what happens is you do a bunch of work hit save and exit. On reopening you'll notice that the most recent capx was a .autosave. If you try to open that it will fail with an error message. The next recent will be the capx you were working on however it wont have been saved.
I suspect the autosave files became read only while google drive uploaded the changes. So it fails to delete and write the next one and perhaps breaks the whole saving process.