Top layer being filled in at normal layer heights

[dsegel]

Slice the model in the attached FF. If the layer height is set to 0.1 or 0.2, it fills in the top layer. If I set it to something else, like 0.0132 or 0.2064, then it slices correctly. Any ideas as to what's going on here? NetFabb doesn't report any problems with the stl file.

[habloIngles]

s3d built in manifold checker shows non manifold edges all along the inside of the model, which I'm guessing is the reason why you're seeing what you're seeing

[dsegel]

NetFabb Basic doesn't find anything wrong with it, but when I ran it through the NetFabb/Microsoft cloud fixer it came back with a membrane in the middle and the threads had turned into intermittent spikes. Weird.