active Flickering ground texture fragments

[Dreamsofwings1]

Something I am seeing in my sim in the last few days, and this is about as bad as I have seen it.  I've just completed a flight where I only saw it briefly in the descent but this video shows a part of a flight where this effect is constant.

Using P3Dv4 with Chaseplane and this is ORBX Pacific Northwest.

Any ideas on a cause of this would be MUCH appreciated!  As the short video below shows as the camera moves around some fragments of ground textures will flicker black.

 

 

[Dreamsofwings1]

Having done some troubleshooting this effect disappears if I turn Terrain Shadows casting shadows off...bit of a shame to have to do that