Currently, several slots on the update UI have missing keybindings so they cannot be changed or rebound. There are in total 12 skill slots that are unable to be bound or rebound to keys.
Also, the skill bar UI will now be invisible if no skills are placed. When dragging skills to your skill bar the slots will be made visible. Once a skill has been placed it will be visible. Any empty skill slots will remain invisible.
Any news or updates regarding these issues will be made on the Riders of Icarus website here: http://icarus.nexon.net/en-US/news