I'm sorry this happened, but Construct is beta software, and so long as it is, we can't really guarantee it's not going to explode. This can even happen in other mature software releases as well, so I guess you learnt the hard way, to make backups, and not to assume that any backups are done for you. Sorry.
Still, all such cases should be reported on the tracker - if you find something you undo and redo and it screws up the cap, obviously that's something we desparately want to fix so it doesn't affect anyone else - a good bug report with reproduction steps will help there.