Items can fall through terrain into the abyss.
I was doing a mission and collided with an item on the ground which in turn made all items in my storage cabin explode out. Pressing R for to activate the scanner showed the name of an item in a place I could not reach.
Another time I let go of an item on the elevator after recently pressing R and the item tumbled off the elevator platform and istead of it stopping on the snow I witnessed it phase through the terrain and it's name going down below (it kept going down forever).
Maybe a hitbox rework is needed>?