Sigmag Thanks. I would have provided more but I couldnt narrow down the issue to provide a capx, while also not wanting to provide my full game capx. I went through your suggestion to no avail, but I did fix it briefly.
I thought turning pixel rounding off fixed it. However, what I did was accidentally export my build to the same directory I hold the source and upload the entire folder to my server. Opps
So I'm not sure what that suggests... perhaps it started using the original images? Therefore perhaps it's caused by using brute png compression? So I have checked my exported tile image, which is actually in a tile sheet now. This is because I use 1 frame animations to put all my differently decorated tiles of the same type into one sprite object. Then at start up I randomly choose one of the animations. Therefore dynamically decorating my scene.
So I guess the next thing to test is playing with different compression levels and perhaps using a tile sprite with no animations and therefore not in a tilesheet. However, I have run out of time today.
I will leave you with this though. My original questions has always really been. Should there be difference between previewing and viewing within the same browser? If so what things are different? What things are applied during the export apart from png compression and minifying?
P.S. It's pretty cool to know that you can kind of create spritesheets by using animations this way. However, it's a shame you can't specify the spritesheet dimensions (or can you?).