I can’t duplicate Items, but maybe I’m pressing to slow. However, this is probably related to the delay you have between your pickup logic and the destruction or removal of the picked item. But if it’s the reason I’m thinking, you should be able to fix this very simple by adding a gate node after pickup which starts opened, get closed immediately after entered and opened again when your pickup logic finished, so the picked up item is is removed before you can pickup again. Ofc, a Do once node will just work aswell.
I’ve just tested it, and its exactly like I thought, if you have a delay between adding the item to the inventroy and removing it, it can be duplicated - the solution is just as I wrote above.