Help leak from my hpa tank regulator

When I try to fill my big bottle my regulator leaks from the gauge....when I seal my bottle the air leaks out the nipple....if I close the valve really tight you can only hear the leak if your ear is on the nipple....I know how to completely disassemble the reg but cant figure out the problem...people says change the o ring on ur fill nipple but my nipple doesnt have a stem....noticed black debris when I disassembled in bottom picture felt like rubber sealent cant tell if it was a oring also....dont remeber which spot the fill nipple goes picture #2 or picture #3....

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