Crank sensor Mercedes sprinter autosleeper

Anyone else experienced this fault. We had new crank sensor fitted purchased from euro car parts it said it was Bosch but not sure it was a genuine part.
The fault came up again after it was reset.
It has been suggested that it was a non genuine part this could be the problem.
Also suggested book in to an auto electrician for a wiring fault.
One garage said we should have a new cam sensor and another new crank sensor.
The van is still starting a bit sluggish sometimes.