Ah, I see. Unfortunately it may be a bug in 3.4.02. It could also be that Apple has made changes to macOS since then and broke Spine's processing of keyboard input.
You might try 3.5.51 and see if the JSON exports are compatible with 3.4. I don't remember if they are, but you might get lucky. The binary exports will be incompatible but there's a small change the JSON from 3.5 will work with the 3.4 runtimes. That's not usually recommended of course.