Dave – interesting, that did the trick.
I used CF3 in Premiere for the color grading. I created a copy of the clip w/o CF3 and changed the clip on AE, then applied the CF profile inside AE and the artifacts have gone away.
On your other point: There are many other aspects of this video that require animation only provided by AE. Otherwise, I would totally agree with you to keep it simple and stay in Premiere.
Thanks,
Jan