Lumintop developed weird problem. Only turns on when loosened.

My copper lumintop tool AA has developed a weird problem. It only works if I loosen the tail cap significantly. I’ve read this is because of loose retaining rings inside the tail cap, so I took it apart, cleaned everything and nada. The retaining ring is bottoming out normally and it still only lights if I loosen the tail cap. I also noticed it lights if I removed the Tail cap and touch the copper the the back of the battery without screwing the tail cap on, but the switch appears to work normally. Any ideas??

by Eisenheim1