So it’s unlikely to be OpenJDK related. Sorry to tell but that’s my primary interest here and I wouldn’t know how to debug your issue.
I’d start ramping up debugging. There’s probably a setting for jetty (the web server) that should get you more information if your issue is really tcp or http sessions being dropped but I don’t know it so you have to search the forum and net yourself please.
(I suggest you open a new thread)