The behaviour is like this -
if you click on a new image then a couple of Ajax call are made and I start a timer and wait until they return. If they fail because of any reason I make a page refresh and you go to the first image you clicked on the thumbnail page.
Sometimes this is because an image take too long to be processed or a request failed.
You could increase the timeout (it is not very long right now) or pregenerate the cache.
Please keep on investigating. Are you willing to test my version 1.8 which is using sprites? It seems you have an eye for even small things.
I will start my official test phase next week but some other tester than myself and my stuff would be cool.
Best,
Michael
btw. Why are you still up? It should be after midnight already in your country?
I know - In Germany it is after 1 already - but this is my time where I implement everything
.