[Neil Harvey]

I know this is an old thread, but I recently came across this problem. One thing people may wish to try is changing your sequence setttings to 10-bit uncompressed. Gaussian blur banding can be a codec related issue, rather than being to do with the effect algorhythm.

Another thing, try placing the ‘Add Noise’ filter before the Gaussian blur in your effect chain. With subtle Gaussian noise, you can also definitely reduce the bands.