Mercedes is still checking for "unknown gremlins" from Lewis Hamilton and Valtteri Bottas's Austrian Grand Prix failures that could cause future penalties.
The team has now confirmed that Hamilton suffered a fuel pump failure that led to him losing power.
While that is not an item associated with penalties, the failure and the sudden on-track shutdown could have triggered issues elsewhere in the power unit.
Bottas stopped with a hydraulic issue, and his engine also has to be given a clean bill of health after he too stopped on track.
The only replacement parts that would trigger immediate penalties at Silverstone would be a new energy store or control electronics for Bottas, but any others would push the drivers closer to future penalties.
Mercedes says that the Austrian retirements were not related to each other, or to the new engine specification that was introduced in France.
"They weren't the same failure, they were entirely different," technical director James Allison explained in a Mercedes video clip.
"On Valtteri's car it was a hydraulics failures, starting in the power steering but being felt ultimately in the ability to shift the gears, which caused his car to stop.
"And in Lewis's case it was a failure of the fuel pump, meaning we couldn't deliver fuel to the engine, and so we had to stop there as well.
"Entirely separate failures, and neither of them in any way related to the introduction of the new power unit."
Allison is confident that there will not be any issues with either engine, but he admits that there are aways some concerns when a driver has to park in a hurry.
"Are we going to have any consequential replacements of parts that might cause us sporting penalties? We hope not," he said.
"We think both of the failures that we had were confined to the items that failed, and they're both things that can be replaced without having to break into the sealed areas of the car that attract sporting penalties.
"However, I say we hope not, because every time the car stops in an uncontrolled way, where a failure happens and the system is then shut down in a manner that is unusual, and the car can suffer all manner of unknown gremlins, we can't be completely sure until we've done all the necessary checks to be certain that the bits of the car that are sealed, and which do attract sporting penalties, weren't in any way affected by these uncontrolled shutdowns.
"So we've got a bit of work on our plates at the moment to try and make sure we're not taking any undue risks with parts that were not to do with the failure, but might have had some consequential damage as the car shut down.
"But we don't think so, we think we'll be in good shape for Silverstone."