Having clouds right inside Corona is a great addition and with a lot of adjustments, can look really good. Maybe this isn't a bug per-se, but a needed improvement for future builds.
One thing that is not realistic and potentially an issue is the size of the sun disk. What I mean is the edge of the sun's visible disc will not be occluded by the clouds unless the CENTER of the sun goes behind a cloud. It's a black and white issue. Either it's completely blocked by the clouds, or it is completely visible in front of the clouds.
This issue can be somewhat hidden with a nice bloom and glare, but you will still get a sudden blocked effect with just a tiny bit of movement.
In this image, you can see the sun is only 1 degree lower and it's completely blocked. In the first image, we should be seeing the sun partially blocked with a lot of light bleeding on the edge. This test was done using r20 (I was rendering in r25) so I will test it in r25 soon.
Mac OS Monterey
C4D r20
Corona v9.0