If my German is correct, then website
http://www.luftkrieg-oberhavel.de/webs/raf/r017.htm
says that the Wellington was shot down by a Flak-unit: 4/514.
Have no experience with look-ups in German archives to see if anything can be traced there.
This Australian story has it that the Wellington had been attacked by a Messerschmitt...
https://vwma.org.au/explore/people/806928
German claim lists may provide an answer if and when Wellington was shot down by a fighter near Oranienburg.
Regards,
Leendert