Hello, I'm a student using SolidWorks. Maybe you can help me with this problem on my assemblies.

I designed 4 parts and wish to put them as an assembly. However, only 2 of them show on the assembly window. The other 2 only appear in the "tree", as if they are on the assembly, but I can't see them on the screen. They won't show. I checked to see if there's a "hide" on them but there isn't.

I tried to manipulate, and put one of the problematic parts first, and then tried to add the others. The first problematic part does show up, but the other one won't- I just get a totally grey screen (and the first one is "deleted").

I attached a picture. You can see the parts' names on the side, 4 names but there are only 2 parts in there.

As you can see the parts are really simple (that's a flute:)).

What can be the problem? I simply don't know how to proceed.

Thank you very much!