On a night when Old Trafford’s concourse caterers went down, Manchester United made an undeniable hash of what had appeared an easy cruise to victory over Middlesbrough. They were knocked out 8-7 on penalties and so unless Ralf Rangnick’s half-cocked side somehow win the Champions League, United’s trophy drought will stretch to six years, at least.

If the unfortunate Anthony Elanga missed the vital spot-kick in front of the Stretford End – the 19-year-old was devastated – this, really, was a defeat born from United seriously losing the plot in the second half.

Related: Man Utd 1-1 Middlesbrough (aet; Boro win 8-7 on pens): FA Cup fourth round – as it happened

Matt Crooks’s 64th-minute strike that levelled out Jadon Sancho’s opener was controversial as it came courtesy of a Duncan Watmore handball ruled accidental and thus legal. But United’s serial missing of chances – including a Cristiano Ronaldo penalty – and failure to control their foe were to blame for the reverse.

It meant Middlesbrough ended a 17-year sequence and beat United for the first time since 2005 and could celebrate before their packed and jubilant away support. For United, though, the questions rumble on regarding where they are headed under their interim manager.

For this fourth round tie Rangnick could select Paul Pogba for the first time, after 15 games out with a thigh problem. The Frenchman lined up on the left of midfield trident in a 4-3-3 Middlesbrough hoped to thwart, via Chris Wilder’s three centre-back formation.

United, though, were in a mode not often seen early in contest: a high ear that tore through Middlesbrough, who struggled to stymie their hosts quick and slick play, the home faithful offering “oohs” as Ronaldo hit a bicycle kick straight at the busy Joe Lumley, Boro’s goalkeeper.

At kick-off Pogba’s season in numbers read 17 appearances, seven assists, no goals, and a red card. Rangnick had been encouraged by his showing in training and a thrust that drew a free-kick, a slide tackle on Folarin Balogun and the dragging of markers around to create space hinted at a keenness for the fray. All of this preceded Pogba winning a penalty after he drifted into the area, took Luke Shaw’s pass and was pulled down by Anfernee Dijksteel.

What occurred next, though, was Ronaldo offering his familiar stock-still standing preparation ahead of the spot-kick before, surprisingly, running up and missing to Lumley’s right, the Stretford End’s cheers of anticipation for their hero muted instantly.

Moments later the disappointment faded. Bruno Fernandes had spurned a close-range chance but now drilled a ball into the effervescent Sancho from halfway. A mis-control took him wide but his effort – deflecting slightly off Isaiah Jones – went through Lumley’s arms and in.

This was a deserved goal for United who were rampant and had cast Middlesbrough as bystanders unable to affect the contest. In Fernandes they had the chief orchestrator, his next defence-splitting ball releasing Ronaldo along a left channel. The No 7 blazed at Lumley and he saved, but the Teessiders were desperate to survive without conceding again before half-time, when they could grab a breather and look to regroup.

They made it, just about: three Shaw corners in succession from the right failing to create a second that would, surely, have demoralised the side seventh in the Championship – Marcus Rashford tingling Lumley’s fingers from the last of these.

Now came the PA announcement which informed the crowd that no food or drink could be served at the interval “due to a technical fault”, causing predictable disgruntlement and a chant of “Glazers Out” directed at United’s unpopular owners from some fans.

Related: Proud Hartlepool out to storm Palace and rise above the monkey business

They could be happier with the hunger their team continued showing in the second half – at the start, at least. Scott McTominay, Fernandes and Sancho hunted the ball down in one vignette yet the message being sent to Wilder’s men would have been more ruthless if Rashford, then Ronaldo, had not spurned chances that were akin to the “gimme” category of tap-in putts for golfers.

This underlined how United’s inability to finish off those in green off could still bite them in the proverbial and cause them serious regret. So it was to prove.

Wilder’s team were enjoying their best phase, illustrated by Pogba having to intervene in his area as Crooks threatened to equalise.

Next the latter did just this though it was a divisive decision from Anthony Taylor and VAR as Watmore, a former United youngster just on as a replacement, handled Jones’s pass before playing in Crooks. It stood as it was not deemed intentional from Watmore but without his hand he could not have found Crooks.

United, though, were in certifiable shooting-themselves-in-the-foot territory. A next hapless moment came when Fernandes hit a post when it was simpler to score, while Pogba’s later header when falling back from a Shaw corner summed up how Rangnick’s side had faded and, ultimately, would lose.