Playing information ping pong. We sent them some issue with a lot of information and instead of actually investigating they often dragged on the whole thing by asking for details they should have themselves, taking hours-days to respond etc before they actually did something. We often had to escalate issues via our account manager.
This was all on enterprise support while I was working for a company that paid six figures each month for infrastructure in their data center.
Regardless of how you host Nextcloud, what you described is one thing I really like about Nextcloud: the major part of it being synced to several devices. As long as you have a computer with the desktop client that's on every once in a while, your stuff is saved across different devices.
I've had a similar thing happen once btw, deleted the wrong server. It was "just" monitoring data, but I had spent a lot of effort building it properly. I eventually started over it, but knowing the whole thing is gone feels really bad.