The Keyboard of my new A04 seems to be warped. With the front piece installed it sits flat, but it was hard to install that piece because when one side of the keyboard was flush, the other side was elevated.
Mine was like this too. I just sorta bent it back (gently) and it seemed to flatten out.
I think the cause might have something to do with how the keyboard was assembled, maybe the plastics were warm and then shrunk a bit?
This was happening to me, too. It took several tries to get the keyboard to snap in and sit flush in the plastic, instead of rising up on one side. Nudging the screen upward to the highest possible position before trying to snap the keyboard in helped.
I took out my keyboard and loosened the outside 2/3 of the screws, then bent it very gently while tightening them again, and now mine is pretty much flat.