Hi Charlie.
Can't find a specific email for you so maybe you can advise.
Looked at your cylinder and doughnut and there is no obvious fault. The
dimension of the DN is different to the ones that work. Yours has a depth of
14.2 mm and jenny's one that just works is 14.7mm. Others I have generally have
a dimension greater than 15mm and these work with no issue. I could reproduce
the leak with other regulators using your DN.
I think your doughnut is just too short and does not reach into the throat of
the valve to seat properly. A new DN is the answer.
Best regards
