During The Witcher 3 you will receive a quest in which you meet up with your fellow Witcher Lambert, during this quest you may receive Grapeshot bombs as loot. If you pick up these Grapeshot bombs they will remain in your inventory even if you already have the upgraded versions.
Attempting to get rid of them normally will result in them reappearing in your inventory, using them and restoring them via meditation will also increase the number of them that are stored in your inventory even though it will display as only having two of them.
To remove them from your inventory permanently you must do the following:
- (Optional) Go to your Alchemy menu and enable the viewing of recipes you have already completed. This will allow you to view the Enhanced Grapeshot Bomb recipe. Under this entry in the Alchemy menu you will see how many Grapeshot Bombs your inventory holds. Keep a note of this.
- Go to your inventory and equip the Grapeshot Bombs.
- Throw them until you have none left. (Preferably in an area where there are no guards or enemies so you don’t get attacked.)
- Return to your inventory and equip the upgraded Grapeshot Bombs you have.
- Drop the bugged Grapeshot Bombs from your inventory.
- Either close the menu and reopen it or switch to a different tab and return to the inventory tab.
- Drop the bugged Grapeshot Bombs again.
- Repeat steps 5 and 6 until the bombs stop showing in your inventory. (The number of bombs I stated in the optional step that you should take a note of is how many times you will need to do this.)
The bombs should no longer be in your inventory. You are now free of the burden of a bugged item in your inventory.