I don’t really think that is an oracle bug. I <b>would think </b>it is some logical error in the application itself.
There are many ways in which an application could cause this hangs, including item triggers (when-validate, post-change, post-text-item,etc.), block triggers, form triggers (key-next-item and others), timers, etc… One event could trigger the execution of some code, and this code could fire some other triggers, and so forth, and this could lead to a cyclic trigger firing; and sometimes it is really hard to find the bug.
I would encourage you to meticulously review you app’s code.