Just updated a resourcepack module to the current 1.11 snapshot and noticed that the shulker_box.png GUI seems to be 1 pixel too high, compared to the other GUIs, 167 pixel instead of 166 pixel.
Attached the fixed graphics to this bugpost, and a video where one can see a demonstration of the wrong height.
Also 3 screenshots ingame with my resourcepack module due to which I noticed it.
Focus on the hotbar, the lapisblock etc., they are "crossing the border" below, whereas e.g. in the Creative Inventory and regular chests or enderchests they don't.
I cut out 1 pixel between the shulkerbox inventory and the player inventory in the attached fixed graphics; it seems to be where the excess height has to be taken from.