Years ago my uncle went along to do spins with his friend who just bought a Luscombe. After several rounds of 2 and 3 turn spins, they tried a 4 turn spin, but it went flat. They couldn't get the nose down, but my Uncle's friend was thinking fast enough to open the door to get as much of his body weight as forward as possible. The change in airflow and CG was enough to recover.
It took a while to discover the cause, but apparently the plane was painted many times by the previous owner and the previous owner never took off the old paint or got a new weight and balance.