Foreword:

Cross-post with this issue

Issue appeared in a custom modpack, however testing was done in a fresh install with only the two mods.

Issue Description:

Inventory sorting is duplicating/removing items while a backpack from Iron Backpacks is open.

What happens:

The backpack functions normally if opened with right click from the hotbar. If opened using the keybind from the inventory however, items placed or removed inside the backpack will be reverted upon reopening the backpack if the main inventory is sorted before closing the backpack.
Video: https://streamable.com/wv2js

My Theory

I think what's happening is that Iron Backpacks copies the content of a backpack to an interface. Upon closing the interface changes are saved to the backpack that was opened. I'm guessing Inventory Sorter is creating a new instance of the backpack when it is sorted and removing the old one. This means that when the backpack is closed the changes are not saved to this new instance and therefore it is reverted to it's previous state when reopened.

Steps to reproduce:

1. Make sure backpack is in inventory
2. Open backpack with keybind
3. Add or remove an item from the backpack
4. Sort your main inventory with middle click while the backpack is still open
5. Close the backpack (with esc) then reopen it with the keybind and your changes will be reverted (i.e. duplication or deletion)

Affected Versions:

• Inventory Sorter: 1.13.3
• Minecraft: 1.12.2
• Forge: 14.23.5.2796
• IronBackpacks: 3.0.8-12