A new one for me: on 13 September 1943, as the HMS Britomart and Russian destroyers were escorting some British transports in Kola Bay, the convoy was attacked by German aircraft. Ltn. Günter Eichhorn of 7./JG 5 shot down a MBR-2 of 118 MRAP covering the convoy, killing the three crew. A Soviet Hurricane flew too close of the convoy during the attack and was shot down by the British transport Empire Fortune. The pilot, Mlaadshi Leytenant Nikolaev, was rescued. No unit is listed for him
Source:
http://www.halcyon-class.co.uk/SBNOreports/sep_1943.htm
German claims and details of Soviet losses from my files
Edited: more on the subject, about two other former cases of friendly fire, with no precise date:
http://www.halcyon-class.co.uk/SBNOreports/dec_1942.htm