Graphics Issue

Hi:
After 40 plus laps in a race my graphics start to play up. Track, fences and grandstands disappear and are replaced with grey to white blocks. Can’t imagine I’m stressing the machine but here are the specs.
If anyone has an idea please share. Thanks.

265GB SSD
Intel I7 7700
8GB DDR 4 RAM
GTX 1080 BGB Video.