Player 1: opened inventory while in vicinity of backpack, moved two stacks of shotgun ammo from his backpack to the backpack in the vicinity by dragging, closed inventory.

Later

Player 2: opened inventory, moved feet to see backpack in vicinity, double clicked one stack of ammunition from vicinity, adding it to his backpack, moved away from the backpack then back, doubleclicked on the second set of stack of shells, closed inventory.

Later

Player 1: moved into vicinity of the backpack, attempted to open inventory, crashed.