Projects with several build plates saved in Orca does open in Bambu Studio with only one build plate, all parts are there but some are outside the only build plate because of the missing plates.
Is this a version problem?
I just updated to Bambu Studio 1.9.1.66 and has never tried to open Orca projects with several build plates in Bambu Studio before.
I also use mostly Orca but it thought i would test Studio a little since there is quite some new things in the latest version.
In this case it was a project with my temperature tests, where i use individual parts instead of stacking in a tower, it contains my own G-Code that i thought i had saved with the project in Orca but that did not show up in Studio either.