Major Cyril Edgar Foggin

I have found conflicting information concerning the following officer, and would appreciate help to find out what was really the case, please.

Major Cyril Edgar Foggin, RFC/RAF; Flt. Cdr., 1 Nov. 1916; 41 Sqdn., 10 Jul. 1918; Capt. (Temp. Maj.), 13 Jul. 1918; killed in car accident, 30 Jul. 1918, aged 26; son of William S. & Elizabeth J. Foggin of Richmond Villas, Haddricks Mill Rd., South Gosforth, Newcastle-on-Tyne; buried in St. Riquier British Cemetery, Somme, France, Grave B.16

The question is that OTF, Vol. 2, No. 4, Winter 1987-1988, states he was with 41 Sqdn. The CWGC, on the other hands, states he was with 40 Sqdn.

Name: FOGGIN, CYRIL EDGAR
Initials: C E
Nationality: United Kingdom
Rank: Major
Regiment: Royal Air Force
Unit Text: 40th Sqdn.
Age: 26
Date of Death: 30/07/1918
Additional information: Son of William Shield Foggin and Elizabeth Jane Foggin, of Richmond Villas, Haddricks Mill Rd., South Gosforth, Newcastle-on-Tyne.
Casualty Type: Commonwealth War Dead
Grave/Memorial Reference: B. 16.
Cemetery: ST. RIQUIER BRITISH CEMETERY

Can someone please suggest which is correct, and why?

Thanks and regards
Steve