GSX never had the ability to select the catering vehicle so, if you are in an airport that doesn't have any score for the catering operator, it will be basically random, which is exactly how GSX is supposed to work: at the same score (even zero), the selection IS random.
However, in the next update, we'll add a feature that will present a menu, similar to the one that selects the ground handler, allowing to choose the catering separately, between all matching candidates.