Jack Redshaw scored his fifth goal in six games to put the Shrimps ahead, opening the scoring as he had done at Barnet last weekend and against Northampton in midweek.
But the game followed a familiar pattern as Morecambe were once again unable to hang on, Bradley Dack levelling the scores in the 52nd minute with his first-ever Football League goal.
Bentley said: "It's disappointing that we haven't managed to win a game after taking the lead in three games.
"When you go into the break in the lead and playing well, it is all the more disappointing when you surrender the lead in the manner we did.
"But I have to give credit where it is due. They (Gillingham) are a top side and played some good stuff despite a poor pitch.
"But we have shown that we can match the best teams in the league when we are at our best and have now lost just once in six months at home, which is really promising for us.
"We looked solid throughout but unfortunately gave away a terrible goal that was a comedy of errors really and you can't afford to give sides as good as Gillingham that sort of opportunity.
"But overall it was a good solid display against a good side and I can't be too critical as some of my players are running on empty now."