First, make sure the face and handle aren't getting stressed by a crooked or unusual installation. Is there anything about the mounting that's pressing against the face? Correct that first.

If that doesn't solve the problem, loosen the fascia bolts with a 2.5mm hex tool and adjust the position until all the buttons and the handle work properly. When re-tightening, do not over-tighten the bolts or else you might crack the fascia/lens. They should be only finger-tight.

I'll create a FAQ entry on this subject. Should have been one for it all along, sorry.