"I simply did not get the start procedure right and did not have it in first.
"A quick reset and we were underway, but it cost the Xbox Falcon a lot of spots."
While the start was a setback, Ambrose raced back up to 10th before the pit stop flurry started. Ambrose handed over to primary driver Scott Pye on lap 56 - the minimum laps required by a co-driver were 54 and Ambrose showed his experience and additional track time at the Clipsal 500 and Australian Grand Prix paid off.
All co-drivers bar one - Andre Heimgartner for Super Black Racing - started the race, the most common strategy play seen in recent years at the 500.
Ambrose described his drive as making "reasonable ground" but seemed frustrated Pye didn't have the opportunity to climb further up the field.
"We did not seem to have the ability to pass other cars from that point to really make more progress," Ambrose said.
"Scott did a great job and was battling for many laps with [Michael] Caruso and [Craig] Lowndes but we could not seem to climb up much further."
Pye - who recorded a top five finish at Sandown last year with DJR and Ash Walsh - echoed Ambrose's sentiments.
"Obviously the start was disappointing but Marcos pushed on and handed it over to me in a pretty good position," he said.
"Everyone was having trouble trying to pass, and we were just stuck in a long line of cars."
While Pye felt Sandown showed further progress for the team, which has steadily started recording consistent top 10 qualifying and finishing results, he believed the team would need to review it's final pit stop and ensure pit processes were like clockwork before the October 8-11 Supercheap Auto Bathurst 1000.
"I think we lost some time in the final pit stop - I'm not sure why but it is something we will have to review in our build up to Bathurst," Pye said.
"Overall I think we showed a lot of positive progress here at Sandown, but we could not convert it to a good result."
The pair finished the race just shy of the top 10 in 12th and Pye sits 19th in the drivers' Championship despite missing the first event of the year.