The only thing that should be getting hot is the atty. The only place you want heat is in the coils.
Take everything you can apart and clean it. Alcohol to get the crud off and if you have brass, silver, or copper polish them where they touch. Check out the spring. You need to get the switch apart and clean it, Like was mentioned look for small bits of metal.
Noalox is a grease, helps threads and other moving parts feel better, and it has zinc particles in it to help improve conductivity. Just a very tiny bit, the more you use the more dirt it will attract, I use a tiny, 1/8 the size of a pea, and use a toothpick to spread it on the threads. You will have to clean more often but it will help conductivity and what you have is a place where there is not good conductivity.