Prior to this UI change, I had left shift key as my auto aim toggle (I play using keyboard only, and using charge attacks, it's a must). This is my first time actually playing with the new UI since I didn't like it from the beginning, I stopped playing.
I came on with some people who wanted to check out the new stuff (dash), and when in the clockworks, I noticed my aim was still auto aiming when I was using the shift key, I went and made sure it was set to left shift, it was. I changed it to something else, and it worked, tried changing it back to left shift, doesn't let me, tried right shift, works.
Seriously, please tell me this is a bug.
I'm not going to even get into the fact that I can't sort my vials to empty spaces...
The vials are a glitch. I can tell you that much. (No, I don't care what you tell me. ;)
At your problem, is the modifier mapped as left shift? That's a new command, and when it's mapped you CANNOT override by mapping that key to another command because it's designed to be held as you map other keys.
Technically, this isn't a glitch if I am to be correct.