This is a
known bug about exiting shop menus.
This happens when you exit a shop menu in any unexpected way (Basically, any way other than pressing the 'Back' button).
So, when you either exit a shop menu by pressing the 'G' key (or any hotkey).
Or, load a save file while currently in a shop menu.
As you said this is easily fixable by simply exiting the shop menu (But you have to exit it using the 'Back' button).