The problem child for me right now is a game built in node.js that I'm trying to host/fix. It's lagging at random with very little reason, crashing in new and interesting ways every day, and resisting almost all attempts at instrumentation & debugging. To the point most things in DevTools just lock it up full stop. And it's not compatible with most APMs because most of the traffic occurs over websockets. (I had Datadog working, but all it was saying was most of the CPU time is being spent on garbage collection at the time things go wonky--couldn't get it narrowed down, and I've tried many different GC settings that ultimately didn't help)

I haven't had any major problems with Nextcloud lately, despite the fragile way in which I've installed it at work (Nextcloud and MariaDB both in Kubernetes). It occasionally gets stuck in maintenance mode after an update, because I'm not giving it enough time to run the update and it restarts the container and I haven't given enough thought to what it'd take to increase that time. That's about it. Early on I did have a little trouble maintaining it because of some problems with the storage, or the database container deciding to start over and wipe the volume, but nothing my backups couldn't handle.

I have a hell of a time getting the email to stay working, but that's not necessarily a Nextcloud problem, that's a Microsoft being weird about email problem (according to them it is time to let go of ancient apps that cannot handle oauth2--Nextcloud emailer doesn't support this, same with several other applications we're running, so we have to do some weird email proxy stuff)

I am not surprised to hear some of the stories in this thread, though. Nextcloud's doing a lot of stuff. Lots of failure points.