Video: https://streamable.com/765g

Statement from officials: https://pbs.twimg.com/media/CxwZ5DKWQAAmgIu.jpg

Using PTS, either one of the officials jumped the gun and hit their button early or it was the table clock operator. But the table guy says it wasn't him, thus throwing the officials under the bus. There is no way to know for sure because as far as I know, the NBA are the only ones who use the PTS system which records all the clock starts/stops and from which source they originated.