I think it's normal if the tank is A BIT wobbly. The tank is fixed on the frame by only on screw (130). This screw doesn't fix the tank itself but a collar (92027). And between the collar and the tank are two soft plastic dampers (92075A) and (92075C). This is to avoid, that vibtations influence the tank directly. In front of the tank are two other dampers (92075), under the tank another one (92075B). But it is only fixed by one screw.