Allegedly, problems were encountered with the redesign effort to adapt to installation of a newly installed cannon. These were not resolved in the summer of 1938; by this point, Czechoslovakia, sensing rising political tension amongst German claims to Czech-held territory, was eager to get more aircraft in the air, Avia decided to use a third machine gun in the nose. Judging by the size of the gun magazine, the nose machine gun was matched with an increased supply of ammunition. For the nation, time was running out and drew to Munich Diktat, at which point Germany commenced its occupation of the Sudetenland (the western border area of Czechoslovakia). Two series were produced Bk-534, cn's 501 – 554, and cn's 555 – 620. Only three of the second batch were completed for the Czechoslovak air force, and the remaining 63 aeroplanes from this production block were finished for the Germans, after the German invasion of the remainder of Czechoslovakia on 15 March 1939.