On a poor stadium:mk pitch, first-half goals from Clayton Donaldson and Jonathan Douglas put the Bees in the driving seat before Shaun Williams hit an 88th-minute penalty consolation.
Robinson said: "I'm frustrated but I'm proud of the fans and the players as well. That wasn't one of our best performances but there was so much effort in that.
"We found it hard in the first half to play out for obvious reasons - we had to go a little bit different because we can't do anything on that pitch. And then second half we weren't again at our best, even in the final third it's just so slow and so uneven.
"The players have got to take two or three touches before they can do anything - it's one of the worst in the league.
"But the boys put that to one side and what they did show was tremendous effort. The disappointing thing is that we put a hell of a lot into it and got nothing out of it."
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