Hammerli pneuma Leak
For fill port leaks, I try a big blast of air in. If there is some debris on that o ring, often this will blow it out. If it persists, it's not hard to fix those type leaks with the proper sized o-ring. If you are hand pumping, won't be able to do the blast.
I've even gotten by with taking apart and turning the o-ring around to the other side and gotten it to seal if I didn't have the proper size.
All those who believe in psychokinesis, raise my hand.
Good judgment comes from experience; experience usually comes from bad judgment.