Sebastian Vettel's title hopes look set to take yet another hit, after a bizarre post-race incident in Malaysia.
Germany's Auto Bild reports that the problem may be a bad batch of carbon pipes.
It all means that Vettel's points deficit to Lewis Hamilton blew out by a further sixth points, despite a stunning drive through the field to fourth by the German.
Team boss Toto Wolff nonetheless called Malaysia "painful" for Mercedes.
"We didn't have the pace to challenge Red Bull or Ferrari," he said. "We need to get on top of why we underperform on certain circuits."
Yet Mercedes's weekend was not nearly as bad as Ferrari's, with Vettel almost running out of fuel at the end before he got involved in a bizarre post-chequered flag crash.
"I think he just didn't look," said Vettel, after hitching a ride back to the pits on the sidepod of a rival's car.
Vettel was referring to Lance Stroll, but the Williams driver was not willing to take the blame for the crash.
"The race was over, so I'm not looking in the mirrors," he told Bild.
The big fear now is that Vettel's gearbox may be damaged, which could cost him a five-position grid demotion this weekend in Japan.
Vettel said that the rear of the car is "very damaged".
As for whether he will take a five-place drop at Suzuka, he answered: "I don't know. We'll find a way.
"It's not my fault if somebody crashes into me."
Indeed, it is believed that Ferrari immediately asked the FIA for special dispensation due to the bizarre nature of the post-race crash with Stroll.
It is also believed that the FIA said that no dispensation would be granted in the event Vettel's gearbox needs to be changed.
Niki Lauda, the Mercedes team chairman, blames Vettel.
"To be polite, crashing after the race is not good," he said. "Why is he overtaking after the race? There is no reason.
"OK, maybe the fault is with both of them. But it could be a more of a problem for Sebastian in Japan."
The Japanese Grand Prix takes place this Sunday.