I had an app which I exported in zip format, selecting "Import setup" as "Create as new".
I renamed an app so that exported app and existing app do not have same name. When I imported, I observed that a screen along with certain formulas were missing if compared to my original app.
Let me know if my export steps were wrong. Else, this is a concern in terms of managing as well sharing apps using export feature. I guess this is the only way of keeping a version control and a backup of your working app and seems like it does not work at the full.
Please see if this needs an urgent fix ! I think it does