HELP! I started out with a traditional greenish 4-coat VP but it was the wrong color when all was said and done - so I decided to use a white casein paint over it to tone it down. It was still too yellow (needed colder blue) so I kept adding layers of the casein with linseed, and at some point added non-pigmented casein size. At this point its flaking and I dont know if its the casein or the lime in the VP or something else. Do I really have to sand it all down and start all over??!!

yes, then prime with Kilz oil traditional