A set of Vapoursynth plugins and script based on the 2007 paper "Reduction of Dot Crawl and Rainbow Artifacts in the NTSC Video" by Ji Won Lee et al., which outlines a technique for temporal and spatial filtering of these artifacts.
Motion estimation and compensation make use of vapoursynth-mvtools.
Compile dotdetect, rainbowdetect and dotblur separately, and process a clip with script.vpy to try it out.
This method introduces significant blocking and undesirable blending artifacts and is not recommended for regular use.