Thanks for all of the details. This is all very helpful information but I'm more confused by the result you report about the new page. If the code on this page preserves the session value for the user id then it should not delete it when it is refreshed. With links and copies of the pages I will be able to look into this further.
I have opened a ticket for you on this, to update the ticket login and visit your support history:
supporthistory.php