Graham Burke was accused of diving as Shamrock Rovers turned a 2-0 half-time deficit into a 3-2 victory over Finn Harps.
Rovers were awarded three penalties in a sensational six-minute second half spell to help turn the game in their favour.
The first one was saved by Mark McGinley in the Harps goal, but Aaron McEneff made no mistake with the others.
Ollie Horgan's side looked to be in control of the Cup tie courtesy of first-half goals from Stephen Folan and Barry McNamee.
Following McEneff's spot-kick brace, Graham Burke netted what proved to be the winner 19-minutes from time.
"The players did right what we asked of them, right from the word 'go'," Harps assistant manager Paul Hegarty told Highland Radio after the game.
"We went and pressed them high up the pitch. We knew we were going to have to score one or two to win this match against them.
"We've had some rough days against them, but tonight puts a tin cap on it.
"We didn't deserve that, as a club or players on the pitch. I don't think we got any justice out of that game at all."
Hegarty felt particularly aggrieved with Rovers' third penalty, which was given after Burke went to ground under a challenge from McGinley.
"100 per cent, he's dived. I have no doubt about that, I was standing looking at it - straight at it.
"I've no doubt he's dived, and maybe that's part and parcel of the game and he's got his penalty, and they won the match so you've got to take it on the chin and move on."
Rovers will play either Derry City or Sligo Rovers in the semi-finals.
Dundalk set up a semi-final date with Athlone Town courtesy of a 4-1 win away to Bohemians.
The lively Michael Duffy had Filippo Giovagnoli's side in front inside two-minutes at Dalymount Park.
But Bohs were level on the quarter hour, with Andre Wright eking a penalty past Gary Rogers.
But Dundalk were back in front ten-minutes before the break when a clumsy Keith Buckley challenge led to a penalty converted by Dave McMillan.
There was more than an element of good fortune to Dundalk's third.
The ball appeared to have passed the by-line by the time Cameron Dummigan wrapped his left foot around it to cross for McMillan to fire home.
Andy Boyle cleared a Bohs chance off the line in first-half injury time, and it seemed to make all the difference.
Dundalk were comfortable with a two-goal lead, and Bohs' frustrations in chasing the game boiled over when Michael Barker picked up a second yellow card in the second half.
The game was put beyond all doubt with three-minutes remaining as substitute Nathan Oduwa made it 4-1.
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