This is not unusual when you free fall the gear it some times will not lock down if you do it at a higher than published airspeed.
Some time back (about 3 years) i wrote to the CAA,s GASIL following a piece they did on the PA34 landing gear, this was the combined wisdom of three long time GA engineers who have all seen most of the problems of opreating this landing gear and would make interesting reading for you.