Many thanks Stig and Leo. It looks like Hans (not Wolfgang) is definitely the victim of GCII/7 in December, and Wolfgang (not Ernst as Kracker and other sources have it) fell to them in January 1940. Probably because there were more than one Wagners in 2 Staffel JG54, although three seems unusual.
The Osprey book on JG54 and
Fledgling Eagles has
Uffz Ernst Wagner as the victim, the latter describing the pilot as an Nco but not mentioning his wounds, but confirming he was a French POW. However the detail that the Wagner shot down on 19 January 1940 never flew again (his foot was amputated) does not correspond to the Leutnant Dr Ernst Wagner who was shot down twice in the BoB and taken POW the second time.
My mix-up with Erich Wagner was not reading my source correctly....
best regards
Keith