Please could I ask for suggestions as to how to keep the contact in my 18650 flashlight. The batteries I’m using are 2 protected PALiGHT 18650s but there is a spring contact at front and back of torch barrel and the springs are pretty pliable meaning that I have to shake the torch every minute to keep contact- presumably at the front where the spring slips off the nipple
that could be a dangerous condition, if the +B spring skews itself to the side and makes contact with +B and the body tube it could result in a short -B to +B. Fortunately most lights are anodized inside so this should alleviate that risk, even though anodize is not really intended to be an electrical insulator.
You use the word "presumably"... I think you should try and solidify that assumption. If that indeed is the source of the intermittency then it sounds like a more stable spring is necessary. Others have used magnets in between the cells to increase the overall length of the cell stack. This could help increase the +B spring compression and better stabilize it.
The other thing you might want to try is rolled up paper inside the body tube to alleviate cell rattle. if the cells are loose and rattling excessively it can cause the +B spring to slip off the nub.