BTW this is not the bug you need to know there is another more deadly one.

Basically users have a random chance to get it by dragging quickly icons in and out of the item slot or accidentally dragging the icon of the item from the shop to your item slot. The icon will stuck on your mouse point and the player will find it very difficult to do stuff. Only way to undo is to exit game and run the game again. Sometimes need to even reboot the machine. I got it myself as well as some others. But so far not sure isolated case or not