Comment 22 for bug 1510009

"atk-wrapper went through some quite big updates between 15.04 and 15.10, so I'd be betting on that being the issue (or it somehow triggering a Java edge case)"

I don't think that is the primary bug. Bugs in Debian and Redhat are much older and look like perfect match to this bug. It feels like a race condition somewhere but I don't know how to debug jvm. Maybe some kind of trace from xcb telling which threads are using which connection would help.