Tandy was at the wheel of their works #6 Porsche Penske Motorsport 963 heading down Road Atlanta's long straight toward Turn 10 while pushing through traffic when a pair of cars made contact ahead and triggered the incident.
Dennis Andersen was occupying the middle of the track and moved slightly right, but his High Class Racing LMP2 ORECA-Gibson 07 hip-checked Triarsi Competizione’s Ferrari 296 GT3 of Charles Scardina.
The contact pushed Scardina sideways before cannoning into Brendan Iribe's Inception Racing McLaren 720S GT3 EVO and Tandy, who spun together with Scardina into the wall.
Andersen was clipped from behind by the spinning Tandy, with all sliding into the gravel trap.
Tandy suffered right-rear damage and appeared eager for a tow out to continue on, but was left unaided for anything other than being put on the flatbed before stepping out of the car.
“It's broken, I can see that,” said the Englishman, who won Petit Le Mans outright with a GTLM class Porsche amid heavy rain in 2015. “If I was a tenth in front or a tenth behind, the car that hit me wouldn't have caught the rear of my car.
“We still had drive, I was just stuck in the gravel. All I needed was a little pull onto the grass, I could drive to the pitlane, and we could maybe repair it. But now we've lost 10 laps for the car to get back.”
He added: “At least we've got it back but it's damaged. We'll try and get it back out. It's a bit of a shame.”
Tandy and Jaminet entered the final round of IMSA's first season with hybrid machinery third in points, only five points behind leaders Pipo Derani and Alexander Sims in the #31 Action Express Cadillac.
“I understand their situation, there's two cars together and we're trying to get them out of the way as quickly and safely as possible, but I literally just wanted a quick tow,” Tandy said of the safety team.
“I 100 percent appreciate what the track workers do for us, it's amazing, but I just wanted to give everyone on this team the best chance to get back out in the race.
“We gave it our best shot.”