Well there seem to be a misunderstanding what backup means and how it should be treaten.
Backup is, in best case, a duplicate of a file and in worst case your original file without the changes of the last saving.
That a backup file can be lost, as well as the original file, is possible. Many external influences can causing this.
To use backup functionality, you normally would edit a file and save it when done, which would then update
the original file. In case of a crash there is a minimal possibility that both files (original and backup) are open and
get corrupted because operating system wasn’t able to close files properly.
What you do seems to be working on temporary files always, so there is no backup functionality.
Regarding the backup every 7 seconds.
Of course, there must be made a decision how often a file should be backed up but one must keep in mind
that shorten the time period means increasing the possibility that the file is open while crash happens.
And if it happens that often I would say you have to start investigating what is causing the crash because
next time it might be that the whole disc is damaged.
Regarding backup functionality lost. Did you check the settings if they are still set?
Cheers
Claudia