Updating to UT 1.8 broke the ability to open backpacks using the keybind when the backpack is not selected in the hotbar. Works otherwise.
This keybind was working with UT 1.5

What happens is with 1.8, if I press (in my case "B") to open the backpack and it is somewhere in the inventory, the GUI opens for a split second and closes immediately. The "call" to open gets canceled, somehow. UT suspected because this is the only mod we updated since that feature was working.