Post-race, NASCAR found that a lug nut or lug nuts had not been properly installed on the No. 20 car driven by Brandon Jones, which is a safety violation under Sections 8.8.10.4a: Tires and Wheels of the NASCAR rulebook.
As a result of their infringement, JGR have been hit with a $5,000 fine ahead of this weekend's action at Bristol Motor Speedway.
How did Joe Gibbs Racing perform at Darlington?
Regardless of their mishap, it was a good weekend for Joe Gibbs Racing at Darlington, starting with the No. 20 car itself, with Brandon Jones winning the Xfinity Series race on Saturday.
Elsewhere, Cup Series star Christopher Bell finished 25th in the same race, with Taylor Gray and William Sawalich coming home in 33rd and 35th respectively.
JGR made it two wins for the weekend on Sunday, with Denny Hamlin winning the Goodyear 400 in the No. 11 after an excellent late pit stop.
Christopher Bell came home third, too, with Ty Gibbs also achieving a top-10 finish.