Spikes under the jaw

When you click on the vertex, you can see all the vertex groups that affect it and by how much.
Starting from blender 2.74 to 2.79, after weight transfer, all vertex groups appear in this list of weights of every singe vertex, even if they do not affect it. Dont know why the developers did this, but ok

Clean tool removes all vertex groups from this list that affect the vertex by the specified value or lower. If you will not remove them yourself, s4s will upon import, but randomly.
Why? Because in ts4 ( and most other games) there is a limit of how many vertex groups can affect each vertex. In ts4 the limit is 4. Sometimes, in places where there are a lot of bones ( chest, skirts), vertices receive actual weights ( not just 0.000) from more than 4 vertex groups. To prevent s4s from deleting a random one from the list, you use Limit total to delete the one(s) that affects it the least and correct the values of other vertex groups