Can't be only bad method to change gears,after the explosion of the engine S&G but after only one curve black smoke.
In my opinion is also bad luck.
Same troubles for me.
I broke my engine after 29-30 laps, then stop and go, and again black smoke from the Maserati V12 after 39 laps.
I could finish the race followed by a deep black smoke.
A very frustrating race for me, I was 5th on the starting grid, then 4th when Andreas went out of the track on the Esses.
On 2nd lap, I spun at the exit of the Corkscrew and became 6th.
Then it was during 25 laps, one of my best ever race : I overtook 5 cars (often because they spun or had troubles) and I ran in first position from (around) lap 23 to lap 27 ...when it became one of my worst ever race : I spun again and broke my engine 2 laps later.
After the S'n'G, I broke again the engine to finish only 6th.