How to convert a SolidWorks 2018 file into a SolidWorks Composer 2018 file without missing parts?

I am having trouble being able to save my SolidWorks file as a Composer file without having missing parts. I have an assembled elevator model, so it has a lot of components in it. When I open the file in Composer it is missing a lot of parts from the assembly. Is it because there are too many parts? Or did something new happen to the 2018 version? This never happened when I had the 2017 version.

SolidworksComposer