Long shot I guess but if anyone use Apple’s implementation of Korean 2-set keyboard you might be able to help.
Sometimes when I type 김 it does not create a sylable block but instead puts the three characters in a line 기ㅁ like that. The first of those two examples was typed in this post but the other is copied-and-pasted from Apple Pages.
When it non-functions is random and seemingly not related to a particular program as I first saw it go wrong in the web version of Outlook and now in Pages.