CrazyTiger6

This is only the case in creative mode because, in creative mode, the item is not consumed when you place it in the shelf, but the shelf still drops its inventory when broken. This seems like intended behavior to me, as lecterns and chiseled bookshelves do the same thing

Upon further examination, my response has changed. It is always the right side of the chest that does not update properly

Not sure what the procedure it for updated information, but I have done a bit more testing following Graymagic27’s response. It seems as though the comparator on the side of the chest the copper golem placed the item in does not update properly, whereas a comparator on the other side updates fine, in order to reproduce the bug, I recommend using a setup like the one in the attached image.