Seems there an error on the customizer. OpenSCAD is also having trouble rendering it when I change the slit length to 62.
UPDATE: OpenSCAD will eventually render it but after many retries. I'm doing this on a pretty beefy MacBook Pro so it's not a resource thing that I know of. I'm guessing it's the fin on the inside of the slit thats causing the problems. The render took almost 12 minutes.