Ian,
It looks to me as if the first (full frame view) shot is not rendering fully because it is essentially a lower resolution thumbnail. When I "supersize" it on my PC, it looks much better but now you mention it, not quite as crisp as I remember. The other photos showing details don't have the option to be enlarged, and appear sharp as is to me.
I don't see the supersize option on my Android mobile device (smartphone), so the first image looks decidedly fuzzy to me on it.
All the best,
Dan.