I have two instances in mind:
1. In of the last two last Big Tyme Classic one-pocket tournaments (I think the last one), he was losing to Tommy Tokoph, and sharked him. Goberto ended up winning that match and the whole tournament. I told a friend of mine in Houston about it a week later, who later asked Tommy about it. Tommy confirmed that Goberto was sharking him and had gotten in his head.
2. In the first set in the finals between him and Sky yesterday, I think they were hill hill, and Sky shot a straight in at his hole to get to 6 or 7, while Goberto was on 5. After Sky shot, he didn't even watch the ob. He got straight up and turned around and told Goberto something...I couldn't hear, but his body language said something like "come on, man, be cool." Goberto was shrugging at him like "what did i do?" To Sky's credit, he ignored Goberto's antics the whole match, but at some point he felt he had to tell him something.