Fixing defective DX lights

Wasn't really surprised, but the Cree Projection that got here occasionally seems to lost contact. With two primaries, especially if it sits for a while, it won't light up unless you open the tailcap and retighten it...or sometimes you can hit it on the side of your hand and it will come on. Clearly bad contact somewhere. The tailcap looks OK; These are Batterystation primaries. Seems somewhat better with Panasonic primaries, but I"m trying to figure out a way to make it more consistent. Any suggestions?

Clean the contacts?
Tighten the tailcap retaining ring?

The contacts were fine but I cleaned anyway. How do you tighten the retaining ring? It seems to have a fair amount of pressure.

There are usually two indentions in the tailcap that let you tighten it. Also, using a washer or paperclip to span the gap between the tailcap and body also helps those DX light's poor connection.

or the retaining ring is too tight, as most DX lights are reverse clicky, if too tight the clicky plunger cannot fully extend preventing the contacts in the clicky from making contact.

I did that last night with my Ultrafire C2 HAIII, i was changing the switch boot to a GITD. and i over tightened the switch into the cap and the switch boot would slightly depress the clicky when it was supposed to be on. so the light stopped working until i loosened the ring.

-ex

Had a similar problem with my MTE rebel100. Rubbing alcohol on all contact surfaces did the trick.