Shift click is ignored

[Nuckerr]

I am having issues where my shift click is completely ignored. I'm running this:

contents.set(pos, ClickableItem.of(getIcon().getItem((Object[]) placeholders),
            event -> modify(tradeGuiProvider, contents, event)));

And when I click normally it works fine however shift clicking, nothing happens.

[Tjorven-Liebe]

I still can relate to this