When in windowed mode, the button coordinates to close the inventory are off. Found when I had my passive skill window open behind my inventory and didn’t want to press “ESC” to close both windows.
The close button appears to be below the actual graphic “X” to close in the top right. Going to fullscreen fixed the issue, but I don’t play fullscreen.
display set to 1920 x 1080
https://i.imgur.com/E5mxxDm.png