Yep, been like this for years... all depends on the particular item (or item location) that the selection cursor is on when you try to close the inventory. If you move the cursor elsewhere you can close the inventory, or alternatively madly spam both the touchpad and the B button). I'm not 100% certain but it seems to happen most often if the cursor is on an inventory attachment slot (such as knife in boot or glowstick on bag etc.)