Did you ever get a ticket number?
I noticed either the same problem, or a very similar one years ago, following an update that was supposed to improve the quality of SSS rendering. I had a character with horns that were intended to smoothly transition from SSS to no SSS and after the update it was a disaster:
I want to say the last version it looked correct was 4.18, but honestly I can’t remember, it might have been even earlier than that. I was never able to fix it, eventually I just gave up and moved on.
Edit: just for clarity, if I remember correctly when I made this character Transmission was not yet supported so this screenshot is strictly about the SSS.