I can't reproduce neither in FF or Chrome.
In both browsers it works as expected for me.
That odd Kyatric, because it fails every time for me.
Are you pressing all for keys the W&D at the same time pressing UP&Left Arrow (this works)
Then all four W&A and the UP&RIGHT arrow simultaneously (this fails)
I am using a Microsoft keyboard but will try this with another one tomorrow to see if it is my keyboard.