@chaton This happens only when 2 smokes are thrown on top of each other. It seems as if the smoke isn't blending, but actually rendering the smoke infront of it out. This is probably caused by the client side smoke issue, where what you see, isn't what the enemies see.
I think it's somehow related to this issue: https://forums.focus-home.com/topic/40763/smoke-fire-effects-combined-look-unrealistic-bad
Please check using Incendiary/Molotov added as well