It may just be some bad luck early in the series. I've always thought KBS does a real good job on their subtitles. Especially for these historical programs where you get a lot of obscure terms, foreign names and other challenges. Hopefully these questions will fade as the series goes on.
Frankly the biggest subtitle issue by far is the incredibly tiny print they use for identifications and definitions. It's horrible. Somebody needs to remind the subtitlers that not everybody watches this stuff on a giant HD screen.