How to fix the volume buttons?

Hi to all, I need to fix the volume buttoms. Those that are on the left side of DHD. When I push over button - it works fine....but, on the contrary, the button + is hardly demage. I must push strongly and sometimes it doesn't work and sometimes it work. If I give an attention look to this volume buttons bar, I can notice that the volume button + is more inside the DHD than the other one.

So Can I fix it or Have I substitute the bar?

How could I do it?

Thanks in advance

MAx