What FOP2 version are you using? I recommend to upgrade to 2.30 if you didn't already. As for the problems, if you can reproduce them somehow, then I can work on a fix, if they are 'random' then it is not possible for me to do anything meaningful. Version 2.30 has some changes that relate to the queue login plugin. As a rule of thumb, if you disconnect via the LOGOUT action, then the queue logout should be done instantly. If you disconnect by closing the browser, then the logouts might take up to 30 seconds or so to be processed.
Best regards,