If the patch is off vertically, in that the never perfectly line up but kind of overlap, or if the patch focuses past infinity or stops moving before you hit infinity, the rangefinder mechanism needs calibrating. It's a really easy fix.
I shot over one thousand rolls of film in my 7ii over a five year period and the rangefinder went out four times, but only very subtly. That's after multiple knocks and falls and one car crash! Others have had worse luck, though.