Mods used: base game (2.0.72), this mod (1.1.0).

Steps to reproduce:

1. Create a new save.
2. Open inventory.
3. Select one of the starting items, e.g. the burner mining drill, by pressing Q.
4. Press Q while not pointing any item (such that this mod's functionality is triggered).
5. Press Q again to un-select the item.

You now have one more of the item in question that you started with. This seems to only happen when the selection in step 4 grabs an actual item, not when grabbing ghosts (while "pick ghost item if no items are available" is enabled).