For example, when renaming the movie Reservoir Dogs, {imdb.certification} returns "TV-MA" rather than the "R" that I am expecting. {certification} does a better job of returning the MPAA rating that I want, but sometimes it doesn't return anything at all even though I know there is an MPAA rating for the movie. Gerry (2002) has an MPAA rating of "R", but {imdb.certification} returns "TV-MA" and {certification} returns nothing.
I pasted together a screenshot showing the kind of results I am getting:

Is there any magic you can share with me that will help me get more consistent MPAA ratings? If there is any additional information, examples, etc. that I can provide just let me know.