have a main weapon on your back and another in your hand
do an action like drink, eat, bandage, ect.... what ever makes you put the weapon in your hands down
wait till you complete the action, and you will re pick up your weapon
try to use the weapon.... it wont work
sooner or later it will randomly disappear
drop the weapon but hitting tap and hitting the red X button
go back to where you did the original action to pick up the weapon