ZF-7201: Zend_Form_Element_File::getValue() only works on first usage
If you are accessing the ::getValue() function of Zend_Form_Element_File more than once during one PHP process only the first usage of the function will return the correct value of the element. All subsequent usages will return NULL. At the end I tried the calling the function on the consequtive lines - with above result.
The actual problem seems to lie in the Zend_File_Transfer_Adapter_Http::receive function. The Zend_Form_Element_File::receive() function only returns TRUE once. That's why Zend_Form_Element_File::geValue() will return NULL in LINE 711 on the second usage.