F1 debutant Piastri became the first driver of the new season to retire after attempts to rectify an electrical issue aboard his MCL60 by fitting a new steering wheel failed.
By staying out longer than rivals on his starting soft tyres, the Australian had risen to 12th when he pitted at the end of lap 12. But the ineffective reset forced his early bath.
Stella has revealed that the attempted reset by replacing the steering wheel had not worked because the fault was located further down the steering column.
He explained: "The electronic damage was further down the line around the steering column. So, the steering wheel wasn't the problem. It was a problem with the harness probably. We are investigating. [It was] Not fixable in a short time."
Norris reckoned he was hobbled as soon as Turn 1, when his car developed a pressure leak with the engine pneumatics. Although, this affected the gearbox more than it sapped power. That forced him to pit every 10 laps so mechanics could refill the system by connecting an airline to the left-hand sidepod.
Given the limited pre-season testing, it was decided that Norris should persevere with the fault to bank data. He finished 17th and two laps down on winner Max Verstappen.
Stella continued: "There was a pneumatic pressure leak on Lando's car. We discovered this leak relatively soon in the race.
"Then we knew that it was possible only to do 10, 11 laps each time before having to refill.
"We decided to stay in the race, we decided to try and stay at least within one lap from the leader within the last 10 laps.
"Then if there's a safety car, try and see if there was an opportunity. We did six stops."
Despite the turmoil, Norris reckoned the early pace of the MCL60 had allayed fears McLaren was dramatically off the pace, with the Briton vying for points before hitting trouble.
Giving his account of the unreliability, Norris said: "I had a good start, a good launch.
"I made up a few positions. Then we just had problems from Turn 1 onwards basically. A pneumatic problem and various other issues, which just brought us out the race more and more. We had to keep pitting every 10 laps and that was it."
Asked by Autosport to single out any positives, Norris joked: "I think the best thing was the mechanics had a lot of pitstop practice.
"That's the biggest positive of today."
He then added: "I think the pace was actually OK-ish today as well. We could have scored a point today, at least. It's a shame we had the problems."
Additional reporting by Filip Cleeren and Adam Cooper
