It seems there is some article by Daniel Orme and Thomas Hyatt ( 2 neuropsychologists) is going to be published in "Human Factors and Aerospace Safety" that claims it was the Barons head wound (from a .303 round fired by a 2 seater) that he sustained in July 1917 that was responsible for his "target fixation" that got him killed in April 1918.
I find this rather questionable, since he shot down another 22 a/c after this head wound occured (more kills than 90 percent of all WW1 aces), not to mention he led JG1 on top of that, doing admin work as well...
Victory's post "wound":
 58 Aug. 16, 1917 Nieuport 17 Houthulster Wald 
59 Aug. 26, 1917 Spad VII Poelcapelle 
60 Sept. 2, 1917 RE 8 Zonebeke 
61 Sept. 3, 1917 Sopwith Pup Bousbecque 
62 Nov. 23, 1917 DH 5 Bourlon Wood 
63 Nov. 30, 1917 SE 5a Moevres 
64 Mar. 12, 1918 Bristol Fighter F 2b Nauroy 
65 Mar. 13, 1918 Sopwith Camel Gonnelieu 
66 Mar. 18, 1918 Sopwith Camel Andigny 
67 Mar. 24, 1918 SE 5a Combles 
68 Mar. 25, 1918 Sopwith Camel Contalmaison 
69 Mar. 26, 1918 Sopwith Camel Contalmaison 
70 Mar. 26, 1918 RE 8 Albert 
71 Mar. 27, 1918 Sopwith Camel Aveluy 
72 Mar. 27, 1918 Bristol Fighter F 2b Foucacourt 
73 Mar. 27, 1918 Bristol Fighter F 2b Chuignolles 
74 Mar. 28, 1918 Armstrong Whitworth FK 8 Mericourt 
75 April 2, 1918 FE 8 Moreuil 
76 April 6, 1918 Sopwith Camel Villers-Bretonneux 
77 April 7, 1918 SE 5a Hangard 
78 April 7, 1918 Spad VII Villers-Bretonneux 
79 April 20, 1918 Sopwith Camel Bois-de-Hamel 
80 April 20, 1918 Sopwith Camel Villers-Bretonneux 
He wasnt the only ace to get fixated on an enemy fighter in WW1, he made a tactical mistake yes, but there seems to be little evidence that the head wound was a decisive factor in his final combat. He was tired to be sure, and his wound did give him trouble, but thats a far cry from calling him unfit to fly in combat. That being said, in WW2 and after, he probably would have been grounded after sustaining a wound like he did, in most air forces.
Anyways, interesting stuff.