Mostert and Telitz had been a comfortable fourth in the GTD Pro class, 14 seconds off the lead and another 14 seconds clear of their nearest rivals with just under 20 minutes to go.
Debris brought the Safety Car out and bunched the pack, setting up a grandstand finish.
On the restart, Antonio Garcia in the #3 Corvette Racing by Pratt Miller Motorsports Z06 GT3.R led Jack Hawksworth in the #14 Vasser Sullivan Racing Lexus RC-F.
Hawksworth got into the back of the race leader at Turn 3 and was deemed to have made avoidable contact and was given a drive-through penalty.
Moments after that incident, the caution came out for the final time when Nick Tandy buried the #77 AO Racing Porsche 911 GT3 R in a tyre barrier.
Shortly after the final restart, Telitz tried to pass the second-placed #4 Corvette driven by Nicky Catsburg, who blocked under braking into Turn 3.
Telitz ran into the back of Catsburg and suffered damage to the right front corner. Like Hawksworth, Catsburg was given a drive-through penalty for the class.
That promoted Telitz to second, but damage to the #15 Lexus RC-F took them out of contention with a late pit stop.
Ultimately, Garcia and co-driver Alexander Sims clinched the GTD Pro class win.
Pfaff Motorsports duo Andrea Caldarelli and Sandy Mitchell were second in the #9 Lamborghini Temerario. They had been second before the penultimate restart.
Third went to Ford Racing duo factory Christopher Mies and Frederic Vervisch in their Mustang GT3, who also benefited from the late drama having been seventh with 20 minutes to go.
Mostert and Telitz were given a post-race penalty for exiting the pit lane when the red light was showing. They were ultimately classified ninth in class.
The outright win went to Earl Bamber and Jack Aitken in the #31 Cadillac Whelen V-Series.R Hypercar.
Despite the late yellows, Aitken was able to stretch his lead to a six-second advantage over the #25 BMW M Team WRT entry of Phillip Eng and Marco Wittmann.
Cadillac bookended the podium with Ricky Taylor and Filipe Albuquerque finishing third in the #10 Cadillac Wayne Taylor Racing car.
This article first appeared on Speedcafe.com, a sister site to MotorRacing.com.