Great diagnosis here. Thanks for doing this.
We'll focus in on the code that recognizes the "older" KMA format. It was upgraded to support more features in Hoster later versions (I forget the exact changed version).
It is hard for even MTU to upgrade all our programs that handle KMA files. We are addressing a way to make it happen automatically when a new version is built of each program.
If you can provide us with 2 KMA files that fail on 4.20 it would help insure we are on the same page with you. An actual test file that "fails" can save us hours of senior programmer's time!
Try and attach them here. I'll remove them once we get them.
If you can't attach here, post that and we'll get another way to receive them.