I can't get difference Boolean to stop being hollow. Intersect boolean is solid but diference bool is hollow on both fast and exact solvers.

Here's the problem:

[![enter image description here][1]][1]


Here's the geometry:
[![enter image description here][2]][2]

Here's the bool object:
[![enter image description here][3]][3]


  [1]: https://i.sstatic.net/USNn59ED.png
  [2]: https://i.sstatic.net/UeFKJDED.png
  [3]: https://i.sstatic.net/kEKcsPPb.png
Project file:
[<img src="https://blend-exchange.com/embedImage.png?bid=DYBLXQmz" />](https://blend-exchange.com/b/DYBLXQmz/)