LT,
The problem may not be with the ground ring not touching. If you have the leaf spring type switches, try this. Screw the KL1 on then slowly loosen the tail cap. If it comes on, then there's too much pressure on the switch and it's pushing the switch away from its ground contact point. I just use different size o-rings as gaskets on the tail to "adjust" the height of the switch.
If the above doesn't work, then screw the KL1 on and remove the switch, then use a piece of metal to close the circuit and see if the light comes on. If it does, it's the switch.
The reason that your paper clip solution is working somewhat, is because by doing that you are actually relieving pressure on the switch.