A while ago someone did a very helpful post on this subject with pictures. Anyone able to post a link-I kept it as a favourite but now I need it the pictures have disappeared!
With a BNC connector it should be just possible with your finger nail to touch the pointy tip of the pin. If you can't it may not reach the socket.
Sometimes in fact the centre of coax will shrink or creep inwards to pull the pin back and cause a fault. So work the coax a bit before checking by bending stretching etc. olewill