Put a storage bus with higher priority than everything else on a crate and set to desired block. Now get an export bus with 4 acceleration cards and export the desired item to the same crate. now place a stack of the desired item in the crate and a single one next to it. now the crate fills up with the item.

video:
https://youtu.be/5prAYjeh7_w

running:
ActuallyAdditions-1.12.1-r119.jar
applied-llamagistics-1.12-rv5-beta-7.jar
forge 1.12.1-14.22.0.2467

Works in singleplayer and multiplayer. only works with storage crates. normal chests and strongboxes from TE arent affected. this is why i guess its on AAs side.

originally found on my server with forge 2444, AA-r119 and applied-llamagistics-1.12-rv5-beta-7 with various other mods.

@Shadows-of-Fire (see this comment for reference) while the Javadoc doesn't specify one way or another, the wrapper implementations in Forge do always return a copy, especially when simulating.

So, essentially neither assumption is invalid. Though it seems naive to return whatever is there without copying in a simulation.

There was a similar issue with RS. This is not on our end.

ok. thanks for fast response. i will open an issue on applied llamagistics then.

refinedmods/refinedstorage#1407 (comment)
That's the issue in question that was resolved on RS's end, if it helps.