Dunning for some open items is not triggering

Hi Experts,

Industry:- Retail Industry, Online shopping

I have a business requirement in which a Contract account should have only one dunning level irrespective of the number of orders and their respective due dates. This is customized using event 300 and..This is the present setup of the system and is working as desired.

Please see the screenshot above,

Now I have a scenario,

for the order 201831536 dunning level 21 is reached. The dunning run has occured on 15.07.2013 and at that time, order 202051809 has n't reached its due date. Mean while customer has made the payment for the order 201831536.

But with the next dunning run, this order 202051809 has n't been dunned anymore, eventhough its due date is crossed. Do i need to check in some events?

Thanks in advance!

Lakshmi.