The reason is that the conveyor only presents the item at the end of the conveyor to the pulling queues, whereas a queue allows any of its contained items to enter any queue at the same time.
So when an item of type 37444 arrives at the end of the conveyor it does not match any of the queue Types. Later the batch timeout occurs at 13120 secs and queue293 releases its type 37537 items. At that point you need to adjust your pull logic to allow it to take a new type and have it fire by opening the input of the queue (even though it is open already - telling it to open will reevaluate the pull).
16 People are following this question.
