I realize this is severe necro, but I figured Its best keep all the discussion in one place. This is the first thread google showed me when I asked. I'm having this issue on a more or less regular basis, every few days. It seems like before it does it, the filename in the Construct2 titlebar changes from .capx to .capx.autosave.
I am operating out of a google drive folder for collaboration reasons. I can't say that Drive has been entirely predictable, so it may be some kind of weird interaction or just Drive being funky.