Sirens flashed and wailed in the back straight only seconds after the field for the third event had left the barriers.

ATC starter Dale Jeffs declared a false start when he had concerns the barriers had opened intermittently.

Stewards opened an inquiry into the matter, but found the barriers did in fact open in unison.

But they hailed Jeffs' quick thinking to ensure the riders and horses returned to the start when there was a delay, which was estimated between "one and one-and-a-half seconds", from the starter pressing the button to release the field and the gates opening.

"When I originally affected the start I heard a click, but the gates didn't open," Jeffs said. "There was a definite time lag between pressing the button and those gates opening."

All horses returned behind the barriers and were passed fit to start after undergoing veterinary checks.

Senior riders Blake Shinn, which eventually won the race on Kimberley Star after it was started cleanly a second time, Hugh Bowman and Tye Angland all gave evidence.

Shinn said he thought his gate "was probably the first to open" in the initial start, but credited his quick getaway with Kimberley Star anticipating when they would open.

Bowman said Cinema Paradiso, which bungled the start, had shifted her momentum back in the gates when the top Sydney jockey had unwittingly anticipated the jump.

"I couldn't say anything was untoward, but it just felt like there was a bit of a delay with the opening," Bowman said.

"I pushed [the horse] into the gates [anticipating the start] and all its weight and momentum was backwards when they did spring open. I didn't feel there was any delay in my gate opening."

Chairman of stewards Greg Rudolph and his panel ordered the ATC to conduct thorough testing of the machines after the meeting.

"The stewards believe that you were of the view there was a slight delay in the gates opening after the activation after the start," he said. "We believe your actions were reasonable in the circumstances.

"The decision was a correct one in the circumstances and it was professional of you to have done that before the field had travelled 100 metres and there was no late scratchings as a result."