younggulch

I made a little mountain and base plate part for a project im working on, and when I put the STL in prepare, it looks normal. However, when I slice and preview, it fills in the through hole in the mountain, but only in certain spots. Anyone have any ideas? Here is the prepare screen after I import the part: Here is the preview layer 21: Here is preview layer 42: Here is preview layer 101: Here is preview layer 171