The issue was a lock-up into the fast Turn 9, Mostert sailing into the back of Payne to send them both off the road.
They were both able to resume inside the top 10, however Payne’s day was further ruined when he was tipped into a spin at Turn 1 by Bryce Fullwood.
Mostert went on to finish fourth on the road but fifth in the final standings thanks to a five-second penalty for the Payne contact.
TV pictures showed Mostert in discussion with Payne and other members of the Grove Racing crew, including owner Brenton Grove and team boss David Cauchi, at the end of the race.
That was an effort to apologise from Mostert who took full responsibility for the contact.
Speaking to the broadcast, he explained that his woes started on the formation lap, was followed by a poor start and then capped off by the mistake at Turn 9.
“I lost a lot of confidence with yesterday’s start and we made some changes to the car to try and make it better today,” Mostert said.
“But for the process of warming the car up I was just out of my window. I didn’t quite get away as well.
“Huge apologies to Matty Payne and his whole team there at Groves and all their fans. We’re racing for sheep stations down there and I was chasing him into [Turn] 9, and just with the little of the aero behind there, or a bit of the cold tyre as well, I just pinched a front.
“And as we’ve seen over many years around here, if you do that at 9 you’re generally going for an excursion.
“I tried my best to find that gap slightly in the fence to miss him, but unfortunately I tagged him and put us back from there.
“I don’t know what else happened to him after that, but huge apologies. It’s one of my mistakes.”
