I've discovered a bug that allows players to stack items beyond the normal limit in Minecraft when using the interface block from the mod. This issue can lead to significant gameplay imbalances and may enable duplication exploits (dupes).
For example, if the modpack includes bags or similar containers, this bug allows those containers to be stacked and exploited, potentially leading to infinite item duplication. This poses a serious risk in multiplayer environments or competitive gameplay.

Reproduce:
build an interface with the hopper

upload multiple items with hopper, such as swords

take one item in the inventory

press shift + right click on the item

Expected behavior:
the item will move to the interface inventory

• Minecraft Version: 1.12.2
• AE2 Version: 0.56.6
• Forge Version: forge-1.12.2-14.23.5.2860

As far as I understand this is intended behaviour.