Also a hot button can be because the battery cannot safely supply the power for the load..for instance ohm's law states my dual coil
.15 ohm build pulls 28A at 4.2v, so I need a batt rated at least 30A cont to be safe. So I use a batt rated at 35A that is safe for this build and my button does not get hot, nor the tube itself..in fact I have to chain vape it for it to even get warm..
I would also install a inline voltage meter and measure the voltage drop without the atty attached...subtract that reading from what your fully charged batt reads in your digital batt charger, or separate voltmeter..if its more than .2v
then I'd replace the switch...top cap pin
should be checked too, unless is hybrid.
Good luck, and vape safe !