The Flashseat issue is a very interesting one and I don't doubt that it has something to do with what we saw last night, but I think the post above is the main cause.
The other NBA teams that use Flashseats are Cavaliers, Clippers, Lakers, Nuggets, Jazz I don't think these teams have had issues with late crowds, having watched recent games involving teams in this year's playoffs (Cavs, Clips, Jazz). It seems to be just a Houston thing.