Sebastian Vettel could be at risk of another grid penalty in Japan after a bizarre crash at the Malaysian Grand Prix.
Title rival Lewis Hamilton has suggested the incident was another example of Vettel making mistakes on track, who now trails Hamilton by 34 points in the world championship.
"Reliability is coming into play but also driving mistakes are coming into play as well," said Hamilton.
"We have seen a couple from Sebastian. Today, for example, crashing into someone.
Vettel collided with Lance Stroll after the chequered flag, with the Ferrari suffering extensive damage.
"At the end I was on the in lap, on my normal line, picking up rubber, doing all my switch changes, shutting down the car and Sebastian came flying by me, pushing round the outside like the race was still on," said Stroll.
Ferrari have already flown the gearbox from Vettel's car back to their Maranello base for inspection.
If it is deemed too badly damaged to be used in Japan, a change of unit would trigger an automatic five-place grid penalty against Vettel at Suzuka.
F1's regulations state that a gearbox must complete six Grands Prix, with an automatic five-place grid demotion if they are changed out of this sequence.
Vettel had received a new gearbox in Malaysia after Ferrari changed his previous one following his opening-lap retirement in Singapore.
Another grid penalty would put the German at a serious disadvantage in his bid to overturn the 34-point deficit he has to title rival Lewis Hamilton.
"That could be another bad surprise this weekend," said Vettel.
"I hope not because it was completely unnecessary."
Hamilton finished second in Malaysia, while Vettel did superbly to salvage a fourth placed finish, despite starting the grid at the back due to a penalty for changing his gearbox out of sequence.
Vettel needs to eradicate any unnecessary errors if he is to have any chance of overturning such a deficit.