Impossible to say from the information you provide, however I would look at the way you process is managing the applications, particularly how it is launching and closing. It's not uncommon to make the error of trying to restart an app too soon after closing it down. Some apps take time to close completely.
Another common problem is in the use of waits. BP must keep pace with the applications and waits are the way to achieve this. Without waits BP will race ahead and problems will occur.