Occasional hangs

I have running Spark 2.6.3 on OpenFire 3.7.0 and see occasional hangs when I try to open chat window. Relogin / restart helps, but these hangs are annoying. I’m not sure that http://community.igniterealtime.org/thread/45198 contain correct answer because I want to keep conversation history (I’m not understood from this answer too: problem is in history files or in other profile data files?).