That was on my previous 19 plate Octavia 1.5tsi se dsg estate, I now own a 20 plate with the same engine, but its the sel spec. I think it was cylinder number 2 I had the misfires on, but when Skoda took it in for a diagnostic, they said another plug was going down, too. Not sure which. Then they tried to charge me for the diagnostic, new plugs, until I informed them that they'd replaced them during its last service, just over a year ago lol. They then appologised, offered to replace the two faulty ones for free, as the plugs were guaranteed for two years. I then paid for the other 2 to be replaced, whilst they were on. I was expecting them to replace all 4 for free, but they said their parts guarantee would only cover the ones that were faulty. Can't get much tighter than that. Unless they didnt change the 4 initially when they said they had, that wouldn't suprise me, either. There was no software update performed by them, afterwards, as far as I could remember. Once the plugs were replaced, x4, engine ran sweet, again. My own view, I dont think the plugs were initially changed, prior to me buying the car, eventhough they'd said they were changed. So at tge point of failure they may have been at least 5 years old. The car had around 65k on the clock then with a fssh. It was on two yearly oil change intervals, ex fleet. Unlike my current car, oil has been changed yearly at around 7 or 8k from new. Which I prefer.