The Equip Player loadout option causes the entire backpack row 1 as well as slot 1 in row 2 to disappear and the backpack screen to become locked and uninteractable.

I received a mythical courier and attempted to right-click Equip Player Loadout on it (Morok's Mechanical Mediary). Backpack screen locks as described, but can be fixed by navigating away and back. This is a consistently repeatable bug.