So after further exploration I have tracked the issue (I think) down to this branch node here
It’s strange I know, but I can hook up everything even event melee into the play montage, I can even bypass the branch and just not do the referee life check and go straight into the rest of the code and even kill the referee without issue. But the second I hook up the branch node it throws the error for the dynamic cast with chief on play montage. Maybe an unreal dev has an idea? I wouldn’t even know how to get their attention.