Possible things. Takeoff flap greater than 15 degrees, airborne flaps reduced to climb flap, flap selector left in up selection due next planned flap would be up to zero. Change of flight conditions, low level turn required, pump flaps and they retract,Now stop pumping reset selector then pump again. The docile aircraft bits very hard, Stall in turn with bottom rudder = spin under Very hard to recover at low altitude. top rudder spin over the top recoverable. I tried it in a Ceres with a full load and we flew away at about 10 feet and a dumped load.
This a possible answer.
Happy flying George