Mesh is active for while, than, randomly disappears

Ive been running into a problem lately where I create a few spheres and a sun for my background in my project and the spheres stay vibrant and detailed with materials added, than randomly the only active thing on screen is the sun I made.

Any clues to help?
-Thanks

How are they placed?
are they blueprints?

we need more info then this to be able to help…