Umpires make mistakes while adjudicating their decisions and it's completely out of their hand. One can only try to reduce human error as much as possible. But getting rid of it completely isn't possible.
Recently, Ian Gould was seen atoning to West Indies skipper Jason Holder after he failed to get a decision right. The batsman was Prithvi Shaw and when Holder bowled a short delivery at him, the batsman ducked and was hit on the shoulder. Gould wasn't convinced about the ball hitting the stumps and gave it not out.
However, the fast bowler was satisfied with whatever he saw and thought the decision can be overturned. He went for a review and the replay showed the ball pitching in-line, impacting in-line and clipping the bails. As the umpire's call came in, Shaw survived a close call.
Had Gould given it out, the 18-year-old would have walked back. The 61-year-old apologized to Holder with a grin. The lanky pacer accepted the apology and also smiled back at the umpire as the two got into a brief conversation.