I don't believe the relationship between them has deteriorated to the point the TV show are now making **** up as they go along without Martin's involvement or say so. He's still a co-executive producer on the series.
I never said they were just making stuff up for giggles, but Martin is not consulted on everything. He was obviously disappointed with the Jaime/Cersei thing for example, and said he did not discuss it with the writers. He is obviously consulted about large parts of the story, but is ultimately powerless I would think. I think I read about scenes being added to the episode he wrote the other week for example.
They have to add stuff, as not much happens in Feast tbh(not TV-worthy anyway), so additions are inevitable.
PS. You say one of the reasons he takes so long to write is because of his involvement with the show, but he took ages before the show was out!