When the hairspring that controls the biro like push click close/open function breaks then the flap will be pushed out and will not latch back in. You have to remove the stronger plunger spring. Once removed the flap when pushed closed will return home under the flap return spring. You need a sucker pad, long finger nails or hook to open the flap again.
As long as the flap returns home to the flush postion the locking solenoid (which does not fail) will still work an lock the flap closed.
Even if you don't have automatic locking set the flap will remain in the closed position and not fly or get sucked open by passing airflow. (Well mine does).