Other mistake: If you find a special ammo type in the game and swap your regular ammo out, the gun becomes unloaded and you have to load the new ammo type in. But say if you're doing it with a revolver like the Nagant, you will start unloading empty casings out of the gun to put the new ammo in, as if you had shot all the old ammo out of it even if you never fired a shot and the gun was full of fresh bullets before swapping ammo. The same reload animation of ejecting spent casings.
Bug: Sometimes when swapping weapons for one found in a watch tower that's on the mattress, the gun set down will vanish except for the action. All the wood furniture, barrel, and stock will vanish, and the gun will just look like the mechanism and action floating there. Swapping the weapons again has the other weapon appear the same way.
Trivia: In one of the shacks, the devs hid an Easter egg referencing Back to the Future 3. In the shack, there is a tarp with the shape of the DeLorean underneath it. Also if you look in front of the DeLorean, on the table is the model train set similar to that of the train set used in the movie to demonstrate the time jump in Doc Brown's model.