Long concave roof structure every third trusses won't fill in?

The problem with the zoom is discussed very much in the forum. The ‘clipping plane’ issue is discussed at length here: zoom & clipping (by TIG).

Even if it does not remove it, the way you work can help you to avoid it somewhat or at least to ease your drawing.
If you look more closely at the file I redraw you, you will notice that where there are several lines of the different elements intersecting, if you close the layers and keep only one or two for orientation, you can easily draw more away, without having to zoom in to draw a line.