Visibility of Ducts

[Beginner Revit User]

Hi Everyone,
Working on a multi story REVIT MEP project. I was wondering up someone could help me. I set the view Model graphic style to hidden to help clean up the architectural background (linked) but when I view it with the thin lines enabled it shows all of the ductwork but when I turn line off lines and areas of ductwork dissappear. Can anyone tell me why this is. All ductowrk is above the ceiling and below the 2nd floor.

I attached pics to explain what I mean.

Thanks

[Beginner Revit User]

oops forgot to attach the images. Here they are.

[jason.martin]

It looks like you gaps are set to some very large size.

Manage -> Mechanical Settings to change the gap size.

jason