There are times when the character sheet doesn't work as intended. Clicking a slot does not filter your inventory. Mousing over an equipped item does not show the cards it gives. You can not click to pick up an equipped item. These seem to be times when the inventory isn't shown by default, but you can scroll down to it. For example, when you first enter a module, and it has the module description and your party's levels, you can drag the screen up to see your character sheet and inventory. These bugs are all present. This also happens after you have collected loot and have moved onto the next battle in a module: you can drag the screen to see your characters and inventory, but the bugs are present.
The devs have said that being able to scroll down from the module description screen is the actual bug. Therefore it's no surprise that there are problems if you do access the inventory that way. (And yes, it would be useful to be able to properly access the inventory at that point...)
That's a bug? That seems like a feature! I've actually thought that it was a really nice touch that you can scroll around and see things like that. It really adds to the feel of the game.