Here's a movie demonstrating how the puzzle works and revealing the design oversight.
One of the pieces had some exceptionally thin edges, which came out kind of wispy the first time so I tried building it in a horizontal orientation for comparison. The new orientation is probably a bit stronger, but the difference isn't compelling. Both parts work about the same.
I will probably start over from scratch because of the thin walls and un-blocked movements, but I consider it a very successful experiment nevertheless.