AC: Losing a race due to a missed shift [Read Desc]

Accident happens around 6:00.
I just got a Fanatec Clubsport shifter and decided to try using its sequential mode in GT3 cars for fun. I jumped into a public lobby (~22 drivers) and qualified 2nd (~2 tenths behind pole, even with a few mistakes). It looked like I could snatch 1st or 2nd place quite easily. Then, going into Hohe Acht, I went to downshift and the car refused. The brief moment of confusion/hesitation with one hand on the wheel was just enough to make me brush the kerb, kicking the tail out and ultimately sending me into the barrier.