Hello,
I have already provided the URL/User/Pass of my Wordpress Dashboard as requested.
I have tried all your suggestions but the problem still remains. The main product image appears twice in some mobile devices and normal in some other.
I have also noticed that a similar kind of problem with the picture not loading (or just about 10% loads) appears in my laptop now, but only occasional...please see the screenshot below,
http://imgur.com/a/95IbY
Awaiting for your feedback
Pam