ripped sky wih 90 degree FOV camera

[neon22]

I've been working on making some panoramas.
For most tgd files its OK but for some the sky is ripped apart.
See attached screenshot.
I have tried
- different positions (in case the camera was inside a rock)
- increasing the atmos sampling to ridiculous levels like 160
but no luck, each render leaves different fractures in the sky.
tgd attached

Any idea what i am doing wrong ?
Thanks...

[red_planet]

Nothing definitive ...but early investigation points to surface layer 04...there may be an element of e.d.s. (extreme displacement syndrome  )

All I know is..if i delete that shader it appears to render fine....Love the "cave" with a light in.. 

Rgds

Chris