Before patch 5.1.0 when using rangers parting gift and then throwing a bomb after throwing the bomb instead of switching back to your melee/ranged weapon it now equips another bomb and the same happens if you dupe a bomb/fire bomb (Grenadier, chaos waste boons, ect) Please revert this change because it makes no sense. Why would anyone want to throw a bomb knowing it has no chance to be duped? You dont unless its an extreme situation which forces you to do that or you are on a class with no way to get extra grenades.
The only exception to this should be drinking a endless bomb potion because its always behaved that way since day 1.