On editing terrain - appear some blue artifacts and process JobProcess.exe makes whole computer slow

2) How can we reproduce it using the example you attached
1 Create new project
2 Add terrain to the scene
3 Try to edit terrain like on attached videos
also see attached images.
After the logs appear in the console - process JobProcess.exe takes 40% of CPU (see image BlueTerrainBug3) and seems this is connected to Enlighten process for terrain