The trigger for the crank sensor is part of the flywheel.
You would need to directly scope the sensor output voltage to get an idea of the pattern the sensor is seeing.
It's possible that the stock dual mass flywheel was replaced with a cheap single mass flywheel that might not be correct for the v50 crank sensor setup.
before pulling the gearbox out you could possibly experiment with modifying the plastic crank sensor mount to bring it closer to the tone wheel.
@c30c30 it doesn't earth to gearbox
