Nico Hulkenberg's retirement from Formula 1's Chinese Grand Prix was caused by an issue related to Renault's new specification MGU-K.
Renault was forced to produce a new spec MGU-K after McLaren's Carlos Sainz Jr suffered a failure in the Australian GP.
The Spaniard had the new unit for Bahrain, but the works team stuck with the original version - only to suffer a costly double retirement when both Hulkenberg and his team-mate Daniel Ricciardo stopped in the closing laps of the race.
Both works drivers and McLaren's Lando Norris took revised units for China, and Renault believes the change triggered a software problem that forced Hulkenberg out of the race.
"It's too early to say exactly what happened," Renault F1 boss Cyril Abiteboul told Autosport.
"But we had the problem in Melbourne, and a very quick reaction in Bahrain for one part only for Carlos.
"We had to push massively on production in order to get more parts, which meant that we had to fast-track some of the process and some of the sign-off that we do.
"And basically something was triggered that we had not had the time to properly sign off.
"It's not an excuse, it's a fact.
"All of the other cars have worked without any problem using the same part.
"We've covered 5000kms on the dyno with that part. It's just for one particular reason we went into a mode which triggered something in the software."
Abiteboul said the glitch can be resolved without the need to rush through a third specification of MGU-K hardware before the next race in Baku.
"We think it's something that is outside of the part itself, we don't think that the part that Nico was using was damaged," he added.
"We think it's a software issue, we think we need to change something on the software to deal with something that was changed in the hardware.
"That's why we were hoping to try and fix it in the course of the race.
"Maybe it was not broadcast, but there were a number of actions that Nico was trying to do. He could not go as far as rebooting the whole car.
"That's almost what was necessary. If you want to drive the car now, you could, it's working absolutely fine!
"It's a typical software problem - you have a freeze, you need to reboot. It's pretty much what we were trying to do on track, but it didn't work."