 The aircraft had handling problems, however, caused by interference of the pilots cockpit with the airflow over the upper wing.This was resolved by revising the wing design of the second prototype, raising the centre section of the upper wing by 2 ft (0.6 m) and removing dihedral from the upper wings, flying in this form in April 1923.Further production orders followed with these modifications incorporated as the Bison II, while some Bison Is were modified to a similar standard, sometimes known as the Bison IA.