Mihail
One B-24 was downed by Soviet aircraft near Łódź and definetelly there were no German aircraft involved. Here is the link
http://www.samoloty.ow.pl/str140.htm, where the story is mentioned (in Polish).
The combat I have written about previously, involved two La, Mustang escorts and a B-17, it occured in March 1945.
After some correspondence with a son of a Soviet pilot I am not so sure anymore they were unintentional.