No inventory data gets copied (works with command blocks, but not consistently)

Video link: https://drive.google.com/file/d/1iCbfXtMjzodCwW6C4GzmRl_04UFD9Jih/view?usp=sharing

To recreate, get any item with an inventory, put something in it, then do ctrl+middle click and place the black down, and no data gets transferred.