I am seeing an issue where if the gamePk is the 2nd game of a doubleheader, then statsapi.game_highlight_data(gamePk) returns nothing.
Some example 2nd games of doubleheaders from yesterday:
gamePK=778179
gamePK=778180
I think this happening because the schedule endpoint is returning multiple games and game_highlight_date(gamePk) is matching against the 1st game, instead of matching against the specific gamePk
Note: game_highlights(gamePk) also returns nothing for 2nd games of doubleheaders, since it depends on game_highlight_data(gamePk)