Noticed with the Mazzatun top there is a bad neck seem. Out of curiosity I began to test other tops that show the neck and it seems to be a problem with a few tops. Tried disabling some graphic settings, my ENB, and restarted my game. I don't remember having this neck seem before, but I log on today and suddenly its there.
I'm also noticing it on a few other characters with visible necks.
A Male Breton as an example.