When I worked on my project yesterday, the editor was saving the event sheets but not the caproj file. After I closed Construct2 and opened the project again, the editor said the project was invalid because all of the event sheets were referencing objects and instance variables not listed in the caproj file. I had to edit the caproj file and manually add the objects and instance variables until the editor could open the project again.
Before I understood the file dependencies, I made a versioned copy of the caproj file and nothing else. While that was a mistake, I wasn't expecting the editor to not save when told to several times and then render the entire project unopenable because it failed to save one file.
I'm definitely going to resort to versioning after this. I'm not crazy about dropbox. It's versioning system doesn't go very far and everytime I had to reinstall my OS, I can never get access to my dropbox again.