I'm having similar problems, one of which is not being able to reset the bone to default position after going back and forth between proportion and skinning is there a button/function for this in CC4 or Blender.

But did you try checking weights assigned to those vertices which "fall down"? Maybe you could still salvage the work you have done thus far in CC.

Assigning weights to the face vertices in Blender would sure work in iClone. But if you guys never worked in Blender it would be a steep learning curve.

Will it work without any problems in iClone if we will have facial rig made in Blender?There is so much to do and learn that i am thinking of finding a freelancer to do it.

There is a tutorial for rigging a face for humanoids in CC, but it's real pain specifically for the jaw which is most difficult to paint.
It's not possible to use a smooth brush for jaw, because in CC the normalize weights would randomly distribute values to bones which should not be involved at all (such as Face bone, tongue, teeth.. etc).
So I bet those vertices which are getting pulled down when you removed weights from the jaw got influence from some other bone. Try to select all of them one by one and see which one is pulling vertices down.

But generally I would scrap all and do it in Blender, where you may balance between head and jaw bones only and getting symmetry on the fly.
There is a learning curve, but at least it does what it supposed to do without hassle and struggle with odd behaviors.

1. hello, i am looking for help, I am new with character creator, I imported my custom 3D character and i am learning to rig properly. I already set some skin weights, but after creating some face profile presets, i needed to change skin weight little bit, but i have this problem:Everytime i deselect, there is this weird deformation, vertexes are changing positions without a reason.I guess there may be some problem with "base pose" as i encountered some bugs during setting head move face profile presets, but i don't know how to fix it. I tried every button i found to reset position of character and everytime it looks good, but vertexes are going down when deselecting at skin weights...
2. [13:20]

   normal position with "Animations -> Remove -> All"

   
3. [13:20]

   jawroot skin weight

   
4. [13:21]

   after deselecting

   
5. [13:22]

   
6. [13:22]

   i need to deselect just a sides of mouth so opening is more natural, but there is still deformation if i select just one vertex..