1.12.2 duplication glitch (paperspigot)

I am on a server that runs 1.12.2 and I want to duplicate some stuff to ruin the economy, the dupe I usually use does not work for some reason and I want a dupe that will actually work

If the server has /ah i can help you duping and you can also do a few donkey dupes

how does the /ah dupe work?