Caustics only working in IR or render select mode

[Otuama]

Hi.

I've got some caustics for a pool looking quite good. 

I've just set the shot off to render and it's not working.

It only works in IR or when render selecting the pool objects. 

I've only got the pool water using caustics and have only got a sun specifically for caustics and have set the pool water to include so it only affects the water.

Any ideas?

Thanks

[Otuama]

There's also an issue with the render

Getting dark flashing blocks in the render