QB Enterprise uses Sybase internally, which is a sound choice, except they also do some kind of crazy file-locking over a SMB share, which can sometimes go wrong and cause issues. They scramble the login/password (and there are tools to do this computation so you can try to connect to the DB directly, but the schema is convoluted, and clearly decended from their old Dos/Win 3.1 roots), and then connect over the network to Sybase.
Network clients crashing can cause issues that are difficult to unwind. It should not be possible to get the database into a state where backups + verification fail if it was enforcing referential integrity, but that seems to be common.
The official tools to get yourself out of a pickle from Intuit are guesses at best. There is a cottage industry of people who will (for a great fee depending on how urgent it is), attempt to recover/correct the database for you, because they have experience peeking behind the curtain and building additional tools on the XML API.
Good luck if you are using EDI or other electronic document exchange with other customers, and you transmit sales order numbers for a few hundred orders in the morning, and then things go pear shaped and QB refuses to cooperate and open the file in the afternoon. Going back to last night's backup means carefully/manually re-ordering 4 hrs of work to make sure that everything lines up, so you're probably in for a late day.
Intuit "officially" supports a linux based server for QBE, but the community seems to thumb it's nose up at it, and offers no support for this configuration.
QB, for many years was a very good price for the SMB market. There was a LOT of pricing headroom to the next best accounting package. Someone @ intuit has figured that out over the last 10 years and they are ratcheting up the price till customers fall out -- figuring it's finally worth it to drop QB for another solution.
I'm aware of a migration from QB Enterprise to QB Online, that after signing up and paying, Intuit basically aborted the process. "Sorry, we don't support doing multiple tax rates for employees in multiple states in the QB Online version, here's your money back". Maybe they fix that eventually, but that's where it stood last year.
QB is a frustrating product, for the inertia it currently has.