Strange alternating colors at Spa only

[The Zman]

Spa circuit (both original & chopper) have flashing colored areas that were not there previously.
It seems to occur in a specific green colored area of the track. Flashes alternate continuously between normal green and red or white depending on which PP filter is selected. Does not happen on any other tracks. Tried re-installing Spa - but no difference.
Any ideas? Thanks

 

[Flibbberflops]

Same as this issue perhaps?
https://www.racedepartment.com/threads/nordschleife-shimmering-trees.169591

 

[The Zman]

Same as this issue perhaps?
https://www.racedepartment.com/threads/nordschleife-shimmering-trees.169591

Thank you very much!!!!!!!!!!!!!!
Your link led me to this link which proved successful -
https://www.racedepartment.com/threads/sol.163844/page-125#post-3007047