The visitors led three times in a bizarre first-half that also saw the home side make all three of their substitutions.
And while Allen was pleased with the battling spirit of his players, he admitted too many mistakes proved costly.
"The players did do well to come back but I don't like coming back," Allen said.
"There were far many individual errors and individual poor performances. The defending at times was shocking you can't defend like that.
"You always want your team to fight back but we never got started. This team has been hard to beat and very competitive, playing some good football and passing the ball on the ground. But those key things were missing."