Penny, are you using an o-ring under the atties? If so, try screwing the atty in finger tight on the problem Reo's without the o-ring. Just to see if they will fire consistently. There should be a slight visible gap without the o-ring, and some liquid may seep around the base, but just try it to see if the o-ring you are using is too thick and preventing reliable contact.
Another thing, as was mentioned earlier (page 1) check with the battery out that the switch contact is centered on the battery. If it isn't, you can adjust its position by hand, you don't have to undo the nipple to move it because the whole 510 center pin rotates inside the 510 connector.
Another thing, as was mentioned earlier (page 1) check with the battery out that the switch contact is centered on the battery. If it isn't, you can adjust its position by hand, you don't have to undo the nipple to move it because the whole 510 center pin rotates inside the 510 connector.