I managed to find a solution to my own question in the Symfony forum.
I cannot call an overridden function because it does not exist. Although for me it is enough to redefine it.
Using
$this->_set('my_property', $p);
Works where
parent::setMyProperty($p);
Causes an error.
note that
$this->setMyProperty($p);
Works great in my class if the method has not been overridden.
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