Light cookie jumping around on iOS

Having some trouble with light cookies on iOS Devices. Using Unity3D 5.2.3f1.

The setup is this: Large terrain, using built in shaders, a light source which is a spotlight with a light cookie.

Everything looks alright on OSX.

On iOS the light cookie texture starts jumping around and being shaky. If the player is close to 0,0,0 then the shaking reduces and it starts looking good again. The further away from origo, the more the light cookie texturing jumps around and gets blocky.

It seems like a precision issue, but I am pretty sure this has only started happening fairly recently. I cannot say for sure when it worked.

This is what happens on mobile device:

The cookie texture is there, it is just mapped wrong. If the light shines on a large texture, the cookie shows up, although even the slightest movement of the camera causes it to jump around wildly.

I assume this is a precision issue, but how can I make it look good?

Any help appreciated.