Yes I am having the exact same issue as you are having.  We create invoices through an existing customer project and the email address is seen in the field but once you click into the invoice it disappears.  This is so annoying and was not happening before the change in layouts.  I wish Quickbooks would just leave it alone.  It's a waste of time when you have to figure out the new changes and how it effects your business.

Hoping if enough people complain they will fix it.