There is a bug with the inventory closing. If you press any other key before you press the Q button to close it, it takes an extra button press to close the inventory.
For instance:
-press q to open inventory
-press q again to close
-press q to open inventory
-press any other key except q
-press q
-pressing q again closes it.
I’ve noticed this too, but i thought it was just me. Apparently not. It’s not like GMTower’s Q to hold system 
I almost feel like it would be better just to press ESC or TAB to exit out of the menu.
or even click on a button that says Close.
Thanks for your report! This has been forwarded straight to our Trello board. You can track its status there (it takes a couple minutes to show up on Trello).