Robinson feels that only "stupid and silly" defensive mistakes prevented them from reaching the quarter-finals.
"It's disappointing," he told BBC Three Counties Radio. "I've said to the players we need to take care of the finer details. Switching off at a set-piece is stupid and silly and we need to learn from that."
Milton Keynes recorded historic wins over AFC Wimbledon and Manchester United before knocking out 2013 finalists Bradford City on their way to the fourth round.