Hardwood floors
 

We are removing hardwood floors from a room and installing them I'm a different room. When we started installing them in the new room they wont lay flush like the old floor did. Seems like would take a lot of sanding to get flush again. Is this normal or are we doing something wrong?

They were probibly sanded and refinnished at some time and as you miss match the boards you are seeing how some areas were sanded more than others.

Over time the hardwood will form to the subfloor. once the floor is down that's it.... Either go over it or replace it. It's not a floating floor.
Sorry but I guess keep sanding the lips if you want to keep it.