Behind second answer from zendesk:
This is not a mistake, it is an improvement to the cloud system that lower end video cards are having issues with. The GTX960m is on the lower end of specifications, then you might have to use the simulation on the lower end of settings, which again in this case might have to be without clouds.
Microsoft Flight Simulator Support Team
Nov 2, 2020, 21:02 GMT+1
My graphics card is gtx960m I think it meets the minimum requirements.
Before patch 5 was released, everything was fine. The clouds were working. Clouds are flashing after patch 5 update. Reducing the settings has no effect on this. This is some mistake.