Version: Neoforge 21.1.209 with Quark 4.1-1 and Zeta 1.1

To Reproduce:
Create new world.
Acquire some boots (/give minecraft:iron_boots).
Equip boots on player.
Click the "Sort Inventory" button.

Expected:
Items in inventory are sorted, equipped armor is unaffected.

Result:
Inventory is sorted and equipped boots disappear. This is not a visual glitch, as the player's armor rating reduces accordingly and re-logging into the world does not bring back the boots.