It took some time but finally got the ratchet operational. Come to find out the internal forgings aren't very finely finished, so the littlest bit of misalignment or grit in the wrong spot will cause a malfunction. Filing, de-rusting, and a thorough cleaning solved the issues. Then I slapped a stub of fuel line on it to give it better grip and cover up the worn knurling.
Here it is next to its 3/8" brother, ready to be thrown into the work rotation.