I failed to recreate this in SP and it does not always happen in MP, but fairly consistently

picking up already slotted circuits in the Logic Unit's inventory can leave behind ghost items where you picked them up from
you can jump through multiple slots with this and basically fill the inventory with ghost circuits that way, too

closing the inventory gets rid of all ghost circuits and trying to pick up ghost circuits gets rid of individual ones
as far as I can tell this is purely visual and does not dupe circuits or even temporarily affect the logic

this doesn't seem to happen anymore in-dev on the latest commit, even when playing on a server, but I'll keep this open until the IE server updates and I can see that it's gone there, too