Crawley's lead at the top of the Premier Division was trimmed to seven points after they went down 4-2 at home to Welling, only their second defeat in 15 matches.
It is not time for boss Billy Smith to press the panic button just yet, but the Reds boss and the majority of a 1,777 crowd will have been alarmed by an uncharacteristically poor defensive display from their side.
Leading through Steve Restarick's 21st-minute opener, Crawley then conceded three soft goals in the space of 17 minutes and rarely threatened to pull the game round in the second half.
The three teams below them, Tamworth, Kettering and Havant and Waterlooville, all won and Smith admitted his side will have to learn to cope with the pressures of leadership better if they are to fulfill their Conference dream.
He said: "We knew Welling would come here and battle and that's what happened. There are going to be a lot more games like that in the rest of the season because teams at the top are there to be shot at and we will have to deal with it."
Injuries to Ben Abbey (groin) and Robbie Collins (knee) meant a first league start for Restarick since November 24 and he struck the opener from close range after Jimmy Dack's left-wing cross had eluded a clutch of defenders.
Keith Sharman flashed a header inches wide moments later and Crawley were worth their lead. But the game changed when Gary Abbott surprised the home side with a quickly taken free-kick from the edge of the penalty area while home goalkeeper Andy Little was still arranging a retreating defensive wall.
Stunned Crawley fell behind on 35 minutes when their defenders were attracted to the ball like bees around a honeypot and Tommy Tyne latched onto Gary Abbott's flick to lift the ball into the empty net.
Five minutes later Welling extended their lead when Russell Edwards was allowed a free header from Tyne's corner and gave Little no chance from close range.
Smith threw on Nigel Brake in a bid to give the home attack some much-needed width, but Crawley lacked ideas and Tyne nearly punished them with two counter-attacks before Tony Rivere beat the offside trap to make it 4-1 in the 74th minute.
Restarick tapped in his second after good work by Danny Carroll four minutes later and Welling goalkeeper Glen Knight made good saves to deny Restarick and Luke Anderson, but Welling deservedly avenged their Boxing Day defeat.
Smith said: "Apart from the goals I can't remember them creating too much. I wouldn't have minded so much if they had scored well-worked goals but they all came from our mistakes although the players weren't happy with the first one because they thought the referee was still moving the ball back.
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