Doesn't look like the upper of your screenshots but the lower one,... 
-> Check the "Vapoursynth Preview" (Filtering lower right corner)
here's a larger view:
When I change the blur to blur12 the blur is larger,...
-> looks fine to me,...
Cu Selur
-> Check the "Vapoursynth Preview" (Filtering lower right corner)
here's a larger view:
When I change the blur to blur12 the blur is larger,...
-> looks fine to me,...
Cu Selur