Eevee currently allows on 256 volume samples which can lead to severe banding issues even with optimized start and end for the volume frustum.
Increasing volumetric_samples fixes those issues.
Demo and file in this twitter thread: https://twitter.com/StefanPWinc/status/1154973548508778496
Another example of banding issues: https://twitter.com/brentpatterson/status/1154042824045678593
The shadow samples are also increased in this patch because I noticed that increasing them changes the look of the clouds, thus the currently limit is too small as well...