Address book strangeness after merging in new domains

I recently merged two external domains into a system.

Since the merge there has been issue with addressing formats.

I have re-applied the Internet Addressing selections and that has fixed the address format for emails that are sent to external addresses (i.e. email address is seen as first.last@domain.com - initially after the merge, users of both newly merged domains were sending emails out as user.po.dom@domain.com even though internet addressing was enabled and set as first.last@domain.com).

Now, we are still having issues with the GroupWise Address Book and sending internal emails is still using the GroupWise address format for some domains and post offices rather than the internet addressing format. I have narrowed it down to this:

The system has the two newly added domains and their POs (let's call them EXTPO1 and EXTPO2) and the original system has multiple domains and its POs (let's call them PO1, PO2 and PO3).

What I am seeing is this:
If I login as an EXTPO1 user, in my address book all of the users for EXTPO1, EXTPO2 and PO3 display as internet address format and PO1 and PO2 display as GroupWise address format.

The same results if I login as an EXTPO2 user.

If I login as a user on one of the original POs (PO1, PO2 or PO3) then the address book is correctly displaying internet address format for all users across existing and newly merged POs.

My first thought is to rebuild the DBs of the two newly merged domains and POs - I did a top down rebuild on each system indepnendently before the merge, but happy to take any other advice.

Cheers,
Dave