My brother had the same with his gen3 dual, he was using a nunchaku tank at about 40w using Samsung 30q batteries and one day it just started getting hot around the bottom battery terminals.
Tried different tanks with different batteries and still the same thing was happening....
He threw it away in the end.
It’s a shame because I’ve had 2 and had no trouble what so ever.
Maybe try cleaning up the contacts or swapping the batteries for something different although I reckon it’s more mod related than anything.