Okay... you're gonna do a test.
First, do a hard save right before beginning, because you don't know what Hroki's weight slider setting is.
Now that you have, click on Hroki. Make sure nothing else is in the way, especially mist/clouds/light beams, etc.
Enter the console command "setnpcweight 100" or "setnpcweight 0". Do the stretchy bits disappear?
If so, then your likely problem is a badly done body mod reconform on Hroki's outfit. The vertex index match-up needs to be perfect and meticulously preserved between two meshes that comprise the bounds of the weight slider range for any given outfit, or else the outfit does what I technically termed a "Polysplosion".

Both 0 and 100 weight values simply use the corresponding mesh outright instead of doing an interpolated morph between the two.
Exit the game, then load the hard save you made beforehand to restore Hroki to her original weight, otherwise you'll have a conspicuous neck seam.