I don't get the laser banks in my inventory, but sometimes they do appear in my roboports. I suspect that something makes them "disconnected" from the companion drone (I use Blueprint Sandboxes that switches active surfaces, and if it happens while the drone is (de)constructing it might confuse it and cause issue), and then they go to the nearest roboport. Unfortunately I haven't been able to reliably repeat it, but it does keep happening every now and then.