Christian Horner has revealed human error was behind the 11-second pit stop that ultimately led to Max Verstappen's dramatic crash with Lewis Hamilton in the Italian Grand Prix.
Pit stop issues in recent times have been down to mechanical issues such as wheel gun failures or cross-threaded wheel-nuts, as Valtteri Bottas suffered at the Monaco Grand Prix.
Verstappen was hot on the heels of eventual winner Daniel Ricciardo at Monza and after going a lap longer on his first stint in aiming to overcut his former team-mate, the Dutch driver endured an excruciating wait due to a problem with his right-front wheel.
This meant that he was alongside Hamilton as the seven-time champion rejoined the track following his own stop a few laps later, leading to the incident at the Rettifilo chicane.
"We had what looks like a human error," said Horner. "We had an issue at the stop.
"The wheel was done up and ready to go and unfortunately the car wasn't released.
"It is a human error. Usually, the guys are phenomenal in the pit lane. It didn't go their way.
"Of course, Mercedes then messed up because Lewis should have been well clear and then they had their issue and that's what put the two drivers alongside each other."
On whether the stop could have mentally affected Verstappen into becoming hot-headed in his tussle with Hamilton, Horner replied: "I don't think so.
"He is a racer, he got a run on the run down into turn one, into turn two, so I don't think it affected his judgement at all."
Technical directive bites for the first time
The slow stop was the first instance of a team suffering as a result of the technical directive issued to slow down pit stops.
In order to build in a human tolerance for cars to be released safely, the automatic trigger to signal a green light on the traffic lights has been changed to a human-activated switch on wheel guns.
It is believed that the crew member manning the wheel gun on the front right failed to press the switch, meaning he then had to retighten the nut and hit the button to give the green light.
Red Bull has been the frontrunner in completing pit stops in the fastest times and when the directive was announced in June, at the time Horner said: "I suppose we have been very competitive, we have got the world record on pit stops and we have had the majority of the fastest stops and it is not by accident. I find it a little disappointing.
"An awful lot of energy is being put into trying to slow the car down, which is what happens in a competitive business. It is something we are used to but I am not losing too much sleep about."
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