Slicing issue, hollow to solid

So I have a model that has 4 open compartments in it, when I slice it two stay hollow and 2 turn solid! No clue why this is happening and it has done it with all different slicer settings. I even opened the original model and ensured there is no reason why slicer would think it should be solid. I've attached pictures of it sliced and pre sliced as well as the stl. Any helps guys?

 

I know you said you checked the model, but the only reason it would be doing this is if something was sticking out into the middle of the compartments. Even if this is a small piece it could throw off the compartment. Try slicing it with Cura or another program and see what happens.