8-bit gradiation I guess some colours & luminances don't gradiate very well.
Try adjusting the levels of the colours of the design sometimes this helps.
Try applying the filter and rerendering the sequence as 10bit.
Or don't blur quite so much - see if you can live with 20 to 30 max on the Gaussian blur filter rather than I expect the 50+ you are using.
or if you have After Effects load the no FX sequence into AE and use a 16-bit project to do the Gaussian blur and export that back to 8-bit which will (or at least it should) produce a much better albeit dithered and ringless version.
Grafixjoe might also have another workaround - maybe he will post an answer for you too.
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