Dual fuel VE2 Commodore LPG shaking

At about 50000km (under new warranty)the car started to give the engine warning light when at idle during driving eg at traffic lights. Idle was becoming rough before the warning light and stayed that way, giving less power on take off. Holden dealer diagnostic showed no error. Switching to petrol returned to normal running but warning light stayed on. After cooling down, on next start, the warning light was off and Holden diagnostic showed nothing. Eventually, I managed to get the car to a Holden dealer while the light was on and the engine idling very roughly. They diagnosed coil pack failure and fitted these. Now, the problem is worse, with the car not needing to be hot for it to happen. Car now just out of new car warranty, but take it that fix must be done under warranty as it's never been fixed. I can't sell the car when it is like this! I hear of other dual fuel cars like this. Even getting the name "Harlem Shake" but no solutions posted. Thankyou