Before this update 1.17.40, In 1.17.30 getting the whole inventory of a double chest is possible by only getting a single side of the double chest. Now in 1.17.40, getting only a single side will not fill up the whole double chest.

During Testing when I tried getting the inventory size I was expecting to get only 27 slot size but I got 54 which is the whole double chest.

But when using setItem to every slot up to 54 it only fills up the bottom or top part depends which side of the double chest you set the items.

You can test this for yourself the addon is in the attachment. You chat !test while standing on the chest.