Java memory/version issue [edited].

[bubbleguuum]

Some years ago, with an older OpenJDK 11 version running on Ubuntu, I had observed a bug where worker threads in thread pools would not be reclaimed, inflating memory up to running out of it. I had to revert to Java 8 then (There was no newer than Java 11).
But it was a long time ago and I doubt OpenJDK 11 still has this issue (which may have been specific to that Ubuntu build).
Other than that, you can try newer OpenJDK 17 if available. The Eclipse OpenJ9 JVM is also great on memory constrained devices: it can use
40% less memory at the expense of being slightly slower (depends on workloads and is of no importance for software such as BubbleUPnP Server and MinimServer).
If it is available as a package, I would suggest to use it.