[siding filling window]

One or more windows in some drawings fill with siding. Even when lined up perfectly in a pair, one window will fill in. I have deleted the window and put a new symbol in and as soon as I position it the siding shows up. I have compared all the info in the object info pallet with other clear windows and it matches.

[Drawing disappears in Projection-Perspective]

Why is it when I try to create a Move Along Path Animation every time I select Projection>Perspective the drawing disappears?