Would welcome advice from resident experts.
Detachable cylinder on HW100 carbine leaking from filling port.
While filling can hear air leaking. When filling probe is removed leakage continues until zero pressure showing on cylinder pressure gauge. Leakage appears to be from the cylinder filling port

Would welcome advice on probable cause & what is required to rectify the problem, including spares required & where to obtain them.

Thanks
Cheers
Al.