The whistler, in his first game since missing Ben Thatcher's forearm smash on Pedro Mendes, harshly ruled out a hat-trick goal for Mansfield striker Danny Reet and later produced a hotly-disputed red card for home winger Matt Hamshaw.
Two goals in the last 19 minutes eventually earned resilient County a point, as Mansfield threw away a two-goal lead earned in the opening 19 minutes.
The Stags wasted an early chance when Alan Sheehan drove a 20-yard free-kick straight into the defensive wall.
But Reet made no mistake in the tenth minute when Alan White's sliced clearance from a Gareth Jelleyman cross fell invitingly six yards out and the young striker hammered the ball into the roof of the net.
The rampant Stags should have doubled their lead two minutes later. Hamshaw raced at the defence and his clever pass put Richie Barker clear, but the ball got stuck under his feet and the striker's eventual prodded finish rebounded to safety off the foot of the post.
They had to wait until only the 19th minute for a second goal - albeit at the third attempt from a Sheehan corner.
Kevin Pilkington saved at the near post from Jelleyman, Barker headed the looping rebound against the bar and Reet pounced on the second rebound to hammer in from close range.
A minute later Ian Ross almost gave County a lifeline, when his quickly taken 40-yard free-kick flashed narrowly wide with goalkeeper Jason White scrambling across his goal.
At the other end Hamshaw, with a long-range drive, and Reet with a low drive which Pilkington did well to hold, might have secured victory before the half-hour mark.
Then twice in the 36th minute Barker went close; his rising drive just clearing the bar before his diving header flashed past the post.
Four minutes before half-time, referee Gallagher angered Mansfield's fans when he ruled out a third goal for Reet - harshly adjudging the striker to have fouled Alan White before lashing in a 20-yard shot.
Gallagher was involved in more controversy on the hour when he sent off Hamshaw after he earned a second caution for a foul on Alan White.
Hamshaw's earlier booking, also for a foul, had gone unnoticed by most of the players and supporters - and Gallagher only brandished the red card after County had restarted play.
The Magpies made the man advantage pay in the 71st minute when Michael Edwards, looking suspiciously offside, prodded in substitute Tcham N'Toya's cross from eight yards after goalkeeper Jason White had led a charmed life, missing four consecutive crosses.
Nine minutes from time Ross' piledriver was deflected to safety as County, outplayed for an hour, took complete control.
The inevitable equaliser finally arrived in the 86th minute, Lawrie Dudfield touching in substitute Stephen Hunt's knock-back from a Ross corner.
Two minutes later Mansfield, on the attack for the first time for half an hour, almost snatched a winner when Jonathan D'Laryea's drive was charged down inside the penalty area
And, in injury-time, substitute Giles Coke's low 20 yarder flashed inches wide as County hung on for a point.