The Bat / Voyager - a dangerous repair database of letters

I have been using Bat for many years, but I cannot understand one thing: why the backup system and the repair of the database of letters work so badly and even dangerously.

Recently, a backup has ceased to be created with the following explanation:
“An error occurred while copying the Inbox folder. Perhaps the reason for this is a damaged index file (.TBI or .EBI) of the letter base. Try to delete the index file of this folder, then reopen this folder in The Bat, and then try again to make a backup. ”

Deleting index files naturally does not help, but for this case there is a folder management tool in which you can do a integrity check / repair.
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So after the repair, the letters from the folders disappear! And it’s impossible to get them back by regular means ... Googling and projing has shown that the problem is not solved :(

Does such an illustrious mailer really have such problems with the most important function - backup? In general, if someone solved a similar problem, I will be very happy to learn about solutions.

ps Such a problem arose in Bata, and then in Voyager.