REUTERS: Formula One champions Mercedes had still to remove a stuck wheel from Valtteri Bottas's car on Monday, a day after the problem forced the Finn out of the Monaco Grand Prix.
Bottas pitted from second place on lap 29 but watched in dismay as time ticked away while mechanics struggled and failed to remove the front right.
The retirement cost Mercedes precious points, with seven-times world champion Lewis Hamilton struggling in seventh, and led to the team losing their lead in the constructors' standings to Red Bull.
"We need to learn so it never happens again. It was bad luck from my side and as a team, it will be a priority for us to improve our pit stops," said Bottas.
"There's no one to blame, as a team we just need to be better."
Technical director James Allison said the wheel nut had been damaged by the wheel gun, 'machined' to the point where there was nothing left to get a hold on.
A team spokesman said the car was expected back at the factory on Tuesday, when the wheel would be removed and properly analysed.
Team boss Toto Wolff said many factors contributed to "a catastrophic failure".
"We need to review the design, we need to review the material of our wheel nut because the mechanics that operate the wheel nut need to do it in a way that you can't machine it off," he told reporters.
"As a matter of fact the mechanic that did that is one of the best, one of the fittest in terms of pitstop speed that the team has. It is never someone's fault. It's always multi-faceted."
(Reporting by Alan Baldwin in London, editing by Pritha Sarkar)