Oh Boy have I ever screwed up. I am almost ashamed to admit my mistake since I know better. I have pulled a real newby mistake.
I have been getting a lot of rejections for blocky pixels or halos or other artifacts.
They are not in my original images.
I work in lightroom, 16 bit, rgb 1998 and my images look OK.
BUT to submit them I use lightroom to batch process them to 8 bit jpegs in sRGB.
My mistake… I did not QC the final images. I know better. I have done this long enough to know that you need to check closely the final delivery files, but… I guess I just expected the technology to be perfect.