Do you have FileMaker Advanced?
It might be useful to enable the script debugger in advanced and use it to step through this script.
If not, it might be useful to temporarily add a Pause script step just before the two Omit record steps to make sure that the correct records are being omitted. You might also check to see if a sort order was specified on the room inventory layout. This script assumes unsorted records so a sort order on that layout could interfere with what happens when you duplicate and omit records.