What I need in order to track this kind of issues is some way to reproduce the issue. The mention of a user trying to forward seems to indicate it might be a problem when a specific feature code is being dialed. If you can tell me that dialing for example *781231231 will lead to a "stuck" call then that is great as the problem is reproducible and we can track log files in order to see why it happens, and if its a bug, fix it.
Calls stuck in a 'random' fashion are not really helpful in order to track the issue down. The idea is to reduce the randomness as much as possible and try to force/trigger the problem so we can catch the error in the act.
Restarting fop2 will always help, as it will clear all internal status and poll information fresh from Asterisk.
If anyone of you have a particular scenario where a call gets stuck or some misinformation displayed in FOP2, please let me know so I can try to reproduce that and fix it.