image effects (blur, etc) broken since 5.3.2

Just upgraded from 5.2.something to 5.3.2f1 (and now 5.3.2p4 also, same problem).

I'm running Unity Editor and my build target is set to iOS. None of the full screen effects appear to be working properly, and it looks like an issue in Graphics.blit - I also have my own full screen effects that worked fine in 5.2xx but since upgrading stopped with same side effects.

Here's my scene in the player without the blur effect:


Here is the output with "blur" effect


Or with "greyscale" effect from standard effects:


Or if I "zoom in" to maximise the player window all it then outputs is a grey screen.

Anyone have any ideas? It seems to work okay if the build target is "Web Player" but not if it's iOS.

Thanks guys, pulling my hair out over this

 

Some more diagnostics...

It seems to happen on all platforms but is actually related to the dimensions of the "play" window's size. I've tried deleting shader cache but doesn't help.

Seems to be a problem with the UV coordinates / positions internally in the Graphics.Blit call.

How it looks if I size the window to match the rendered output:

As the window gets slightly too large you can see the right hand side is stretching presumably as the UV coord maxes out at 1.0f


Even wider:


Happens with all full screen effects calling Graphics.Blit.

Any ideas / solutions? Or has anyone written an alternative to Graphics.Blit?

 

Same issue is discussed here http://forum.unity3d.com/threads/bug-image-effects-are-broken-on-5-3-under-osx-el-capitan.385660/