I've not heard of this issue before so I expect it's not a bug with the figure but something going wrong in your workflow for creation of the new morph.

I suspect you are exporting the base figure with Mouth Realism HD and Naval morph on. These two morphs load on a default Genesis 3 Female figure. You can check if the Navel morph is the source of the issue by dialling out that morph when you have your new morph applied and see if the look returns to normal.

Before exporting remember to check the Currently Used section on the parameters tabs it will show all the morphs applied to the loaded figure