Can you state what those reasons are? We know the police were responsible for staging Sheila's body in the right photograph. You can see that the police moved the body by about six inches. The bible has also been moved.
Who's to say that both photographs don't show Sheila's body as it was staged by the police?
Given they were messing around like that, accidentally shooting Sheila when she was already dead is a realistic possibility.

Harry if I agree with you I have to ignore Dr Vanezis' pathological evidence and the evidence of police surgeon Dr Craig.
Dr Vanezis said the two gunshot wounds to Sheila were fired within seconds.
http://jeremybamberforum.co.uk/index.php?action=dlattach;topic=156.0;attach=168Dr Craig said all victims, including Sheila, could have died at anytime during the previous night. (Point 38 from 2002 appeal).
I hope you will not be disappointed to learn that unless experts provide new testimony I am happy to rely on the evidence of the two doctors.