Hi Lee and PMullins,
An update: the MacOS I am using has been updated to 11.2.1
Using the same test image with the same settings in Affinity Photo, with Canson paper and their specific v4 printer profile applied as detailed in my January 5 Post, I tried another test. This time, no problems - no yellow and cyan only issue that I saw before. I can only assume that Apple fixed a bug that they would not acknowledge as one.
Going forward, I am a little skittish and will be doing tests before loading up the Canson paper. As PMullins said, very expensive paper to be throwing away. If the v2/v4 issue pops up again, I will add an update to the thread.