- if you have a tall mod GUI (e.g., FNEI) and a wide mod GUI (e.g., YARM) in the same GUI container at the same time, it creates a large area of the screen that can't be used to interact with the world, despite not containing any active UI. Example screenshot:

The original reporter says this worked in 0.17.34, which to me suggests this may be related to the change in 0.17.35 that added scroll-panes to the GUI tree -- specifically, that these scroll panes aren't click-throughable whereas the flows they replaced were.