Animated textures progressively becoming more pixelated on android.

As the title suggests. I'm using the shader from here: http://wiki.unity3d.com/index.php/Shield

I'm using the 3.3 and IOS version a bit further down the page.

All I have is a sphere which scales up and down with a material applied that uses this shader. The shader has a texture slot so i put a texture in it and it looks very nice. It also has a speed setting to control the speed at which the texture scrolls across the object.

I Build and Run to my Nexus 7 and it looks lovely. I looked again after a minute or so and noticed pixelating. I left it longer and it gradually got worse and worse. Leaving it for several minutes shows the texture resolution is slashed to something miniscule, to the point where the scrolling texture is now visibly made up of about 50 pixels, you can actually see the squares. However the sphere carries on scaling smoothly so it shouldn't be due to slowdown or performance.

I must confess I'm new to shaders but I assumed picking the 'optimised for ios' version of the shader would be a good choice, despite me working on android.

Has anyone come across this and can you help me? It's a fairly fundamental effect needed for our game.