I use the Under Constrction plugin as I often do to work on the page before it is published.
For this I use a custom page that does not contain a header or footer. On the actual page I use custom header and footer. As long as you are logged in, so far so good.
However, when I give the customer the option to log in to the Under Construction page using a password, the custom footer is missing and only the default footer of the respective stack is displayed!
I noticed this missing footer only with version 6 and also in the last version of pro 6.1.5!