Did u try changing the o rings? that might be it or the bottle head needs replaced. my teamates andy and steve have the 98C and when the put the bottle on and take it off it leaks for like a second then stops leaking. Hope i Helped.
I suggest that you have a local shop check over the tank. It might be that the valve on the tank is damaged. It would be easier to have them check the tank first than to spend money on things that didn't need to be done in the first place.