I used the opportunity of your reliability failure to make a larger point about reliable software. I admit was deliberately provocative and terse in the posting, but I have futher clarified things in the comments. I thought about writing a long, detailed, well balance article about this. But that wasn't going to happen, I don't have the time. But then I thought why not just write what I think, but not everything I think? So I did.

Sorry, I might be completely wrong about the source of your problems, I am definitely theorizing as to what you are seeing and I don't think I've implied otherwise. But I will say these are the sorts of things that crop up again and again in Java and other GC'd mutable state languages.

Good luck debugging the problem.

I manage state via relational databases, and haven't had to deal with any memory-leak bugs. I even found it easy to prevent leaking of database connections.

Mutation is definitely optional. A lot of people even still count Lisp dialects among the functional languages.

Your argument construction is not very reliable either. You're basing "large points about reliable software" on... on what exactly? You can't overgeneralize like that, at least not while remaining convincing.