The funny part was that Serena got her ass handed to her in the first set, mostly due to her low first serve percentage, and a higher than usual number of unforced errors.
Only when she screamed out and was penalized for a point at the start of the 2nd set for hinderance, did Serena's game start showing signs of life, but that was mostly from the adrenaline rush caused by her rage.
Once that wore off, Serena started hitting sloppy again, and Stosor settled down and closed out the match.
I'm sure that Serena may blame her loss on bad officiating, but from my viewpoint, she was beaten by a player that was more fit, serving better, and hitting a greater variety of shots on this particular day, while Serena seemed flat from the get go.
ADG