Bastuck shakes in wet weather

Hi! Since recently my Bastuck shakes and shakes off Kat during wet or rain rides. Not permanently, but now and then… the whole seat vibrates with, really unpleasant. Also he squats something short, I guess water. Do I see nothing, screws are also fixed … so, what else can it be? At Audi I have seen that they also have the problem. Through the water he pulls himself together extremely hot exhaust and then strikes somewhere on the chassis … only where can this be with the Civic? Space has enough in all directions and I can hardly imagine how he should stretch in about 3cm!? Ciao Andy