2014 Missing lines in section cut


I use AutoCad MEP 2014. I am going through my drawing and cutting the sections and elevations I need to show. For some reason one of the sections is not showing all of the content that should be there. I have attached 2 pictures as examples of the sections that I have cut. Both of these examples are in the same drawing. Can somebody please explain to me what is happening with the section that is not showing properly. You’ll see the difference when you open up the examples.
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