Shortly after pitting for fresh rubber, the Mexican, who was carrying out his race simulation at the time, reported an issue with his left-front wheel.
Told to try and continue back to the pits, Perez obeyed only to stop again shortly after claiming that he feared the wheel was going to come off.
The stewards subsequently reviewed the video and audio of the pit stop and heard from both a team representative and Perez.
The stewards determined that the car was released in an unsafe condition in breach of Art. 28.13(b) as the wheel was not properly attached to the car when released.
"Unusually," they said, "the wheel clamped to the car and it was not immediately apparent that the wheel was not fully fitted".
The Stewards had the Technical Delegate inspect the car, and his conclusion agreed with the team's that although the wheel clamped, the wheel nut was cross threaded.
The driver stopped the car in a safe manner as soon as the above became apparent to him, and while there was some confusion on the radio, the team gave appropriate instructions as soon as they realized the issue, which was not apparent until just before Turn 9.
Consistent with previous decisions of a similar nature, the stewards decided that a grid place penalty would not be applied as all appropriate measures were taken, and in particular it was not obvious that the car was unsafe when it was released.
"Nevertheless," they said, "it is the responsibility of the team to take all measures to ensure that the wheel is fully fitted" and accordingly, the team was fined 5,000 euros.