Meh..... it almost sounds like the PIR's are staying active for way too long after you have walked past them, which kinda brings some obscure things up.
Are the PIR's fed directly from the AUX 12volt supply?
Neither 12v or 0v wire is fed from any of the panel outputs?
Do the sensors operate correctly when you view them in engineer mode. (Engineer utils....View zone status), do they go active and then back to secure reasonably quickly when you walk past them?
Your exit mode is definately TIMED? I.e the exit sound continues AFTER you shut the door behind you, couldn't be youve set 'Exit settle time' to zero and its arming when you shut the door? (with the pir's still active)