I don't actually use the xara backup; main reason is that historically I had XAR files with the same name in different projects and the xara backup cannot differentiate, so I use a different [ third party] method of backup
I see you had issues back in may :
https://www.talkgraphics.com/showthr...Designer-Pro-X
I would agree with acorn, it is pushing your luck to have more than a couple of files open at a time and rely on the backup to save without also doing a manual save
why did your program stop doing what it should be doing, as set in your options>backup tab ? it seems to me there is something wrong with your system
if there is no backup and no manual save, there is no file; unless you moved the backup location on disk recently in which case it might be in the old location
it might be as well to check your disk for errors and your windows OS too