Stig,
Yes, I had already noted the problem with some of the 17 Sqn losses.
One of the difficulties is that there is no record of events for 17 Sqn for June 1940, just a summary of events for the period 1 May to 31 July 1940:
https://discovery.nationalarchives.g...ils/r/D8408906
which does indeed quote 7 June 1940 for the losses of Emms and Whittaker - but no serials are given.
As you will be aware, these summaries could quite often be compiled some time after the events.
Inspection of the casualty files (non-digitized, so a visit to Kew required) might offer some more clues as to why they are listed on 6 June 1940.
The AM78 cards only serve to confuse the matter further:
P2905 is listed on the front as SOC May/40, and on the rear as FB O Missing 6.7.40 (which will be no doubt from where the information in the Air-Britain serials list was derived)
P3472 is listed on the front as SOC May/40, and on the rear as FB O Missing 6.6.40
Andy