i have found that this setting helped alleviate my issue with FOP2 freezing. please try this if you are testing and hopefully it works. Although i do not have a very high volume, only 40 users, it did help:
; Setting poll_status_mode to 1, will make FOP2 ignore most manager events and instead just monitor the DeviceStateChange
; event and poll for Status every time one of them is received. Experimental mode for high volume systems.
;
poll_status_mode=1
