In newer versions of Minecraft, right clicking something that can be worn exchanges it with the proper armor slot. Because of this, when holding the backpack item it will go into the chestplate slot and switch out whatever is in said slot when right clicked. If you want to open it, you have to take off your chestplate which is really annoying. If this could be fixed that would be great, like for example a seperate keybind for opening the backpack would be good.