United were in East London looking to get back to winning ways as they came up against league leaders Leyton Orient.
And in the end it was a double deflection that sunk the Blues as the hosts took the encounter and the points.
There were four changes to the team that started at Gillingham with Paul Huntington back from injury at the heart of the back line.
Forest loanee Fin Back was in on the right hand side, with Kristian Dennis and Alfie McCalmont also back in the fold.
Both teams started at a high tempo and it was United who showed first with a run from Armer that brought a deep cross. It was cleared, but at a cost, as skipper Morgan Feeney stayed on the floor. It was later confirmed that he'd suffered a hamstring injury.
Ben Barclay was his replacement, with the Blues very much on the front foot. A lovely move involving Back and McCalmont carved a way through and Dennis was unlucky as his flick was smothered by Vigouroux.
The O's looked left and right to get deliveries into the area, but the defence stayed calm as they dealt with everything that came their way.
The Back - McCalmont link-up was in effect once again on the half hour as the right back overlapped. He had Moxon in support but he delayed his pull back and it was put behind for a corner.
Back's influence came to an end with 39 minutes on the clock when he signalled to the bench that he had a problem - also later diagnosed as a hamstring issue.
Orient had half a sight when Hunt skewed a wild attempt over the bar, and Gibson was close with a 23-yard free kick that swept just past the upright.
Into the second period and Holy was down smartly to save a Sadlier snapshot, and he pounced forward to smother it before Kelman could strike.
Moxon sent a free kick from distance over the bar, with the game finely balanced, and there was more work for Holy to do as he made an excellent stop from a Moncur volley.
A sliding tackle from Huntington on Smyth brought loud appeals for a penalty, which were ignored, but the increase in home pressure brought a goal in unfortunate circumstances.
Sotiriou angled a run from the left, and his low drive took two changes of direction before spinning past the wrongfooted Tomas Holy.
The O's were reduced to 10-men for the last 15 minutes when Kelman picked up a second yellow for a late challenge on Mellish.
And Mellish dusted himself down to burst through on goal in the next attack with the ball at his feet. He skipped past Vigouroux but he miskicked and Beckles lunged to clear.
It was the last real chance of the day and it was a disappointed travelling outfit when the final whistle blew.
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Goals
Leyton Orient - Mellish og (73)
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Bookings
Leyton Orient - Kelman (33 & 76 - sent off), Beckles (89), Vigouroux (90)
Carlisle United - Armer (31)
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Teams
Leyton Orient - Vigouroux, Smyth (Lyden 80), Moncur (Drinan 79), El Mizouni, Pratley (c) (Brown 45), Beckles, Kelman, Sweeney, Hunt, Sadlier (Sotiriou 70), Turns. Subs - Sargeant (gk), James, Brown, McCart.
Carlisle United - Holy, Feeney (c) (Barclay 8), Huntington, Mellish, Back (Gibson 39), Guy, Moxon, McCalmont (Robinson 67), Armer, Patrick (Edmondson 67), Dennis (Garner 67). Subs - Kelly (gk), Devitt.
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Match officials
Referee - Benjamin Speedie
Assistant Referee 1 - Joseph Stokes
Assistant Referee 2 - Daniel Cook
Fourth Official - James Vallance
Observer - Keith Hill
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Attendance - 8,713 (1,177)