It seems that his lung problems went a long way. He had caught silicosis from working at the mines. I assume that's why he was turned down as unfit for serving in the Civil Guard, despite his good physique.
His death has had a good coverage in the press in Spain. One obituary pointed out that, when making Mario Bianchi's snake movie, Braña was so apprehensive at making scenes with snakes that he did the scene drunk!