A SF340's main cabin door would not open until the lower part of stair hand rail was gently pushed. The unusual operation could be a safety hazard.

Narrative

After parking the plane at the terminal the Flight Attendant could not lower the stairs. Neither the Captain nor I could lower them either. They simply would not extend. The Captain called Maintenance who suggested pushing the lower part of the hand rail and they extended easily. This was the first time for the day that we had tried to lower the stairs. All previous boarding and disembarking had been accomplished via a jet way. The same thing re-occurred when we landed at the second airport. They opened immediately when gently pushing out on the lower portion of the handrail. [There was] something quirky with the stairs. In retrospect we should not have departed after the first time the problem occurred; we should have called Maintenance to correct the problem. It was a subtle problem which was easily overcome by applying gentle push to the lower portion of the handrail. Without that knowledge the stairs could not be lowered. What made this problem insidious was the nature of it. It was very easily dealt with once you knew you had to push on the lower part of the handrail to get the stairs down. Without this piece of information; it presented a safety hazard. If deplaning quickly in [an] emergency evacuation was required by anyone who did not know where to push; [this would be a problem].