The B747-200 and BAe 146 a/c are the two most common culprits of this "phenomenom". The 146 in particular has an AFGS system which allows the pilot to DISARM the selected altitude whether in manual or auto-pilot flight, by pushing or switching certain buttons, toggles etc when the a/c is in the "FLARE" mode. The newer RJ a/c have dealt with this problem!
It is very dangerous to the inexperienced 146 pilot who does not fully understand and/or comprehend the system.