In my Widget I have a function, OnKeyDown. If I press Tab (the chosen button) it works as it should, but it does not register a second input. This might be the nature of OnKeyDown override functions, but is there any way around it?
Oh, and I cant use a cast from my player character as I have “Set input UI only” as there is a bug that forces you to click for the mouse to go away after you have hidden the cursor.
It seems this is a problem with Tab pretty specifically. I get all key downs as far as i can tell. In the past to get Tab I had to use something like the PlayerController to capture an event for tab and pass that along.
This is a known issue and has a lot of complaints running around. I have not checked if this was resolved in 4.8 but the bug has been around for many months.
Not the response I expected but thanks for informing me! I guess I will switch to another button until they fix it! The only button that does not work, I pick </3
For now anyone who wonders, you cant use tab, switch button 
How did you get “OnKeyDown” event?
in your widget/class go to the Functions area and click the Override button that appears when hovering near the + symbol. Override the OnKeyDown