Animation and physics related bug
That's happened both with zombies, or players corpses in Office Building in the middle of Chernogorsk (near monument) or in tenenment buildings on North side of Chernogorsk, Chapaevsk etc.
Bodies just sticks to walls, or rise up on ceiling and sticks there after death.

Also you can die in tenenment building due texture bug, and your body can stuck on floor or cieling. In this case, your body unable to loot, or you must find point, where your body become lootable, but point location can be behind wall, roof, or anywhere else outside.