OK...for some reason I cannot edit or delete the original post. What I WANTED to say was that it's connected but only via the booking number and is still not picking up the folios connected to the reservation number. If I connect via both, that gives me a blank set.
Unfortunately, the reason that won't work is because the source_id can be either the booking_number or the reservation_number. So joining based on one drops all the folios where the source_id matches the other. That was the reason for my attempt to build some sort of "connector" table that would gather up all the possibilities for the source_id while still joining them back to the original booking table.