*update* DUE to changes in Mixamo it is now better to use Genesis 1 in mixamo, load into daz and save as pose preset. This Pose preset can be used on Genesis 3 and Genesis 8 (if you have the free G3-G8 Pose converter found at https://www.deviantart.com/agentunawares/art/G3F-to-G8F-World-s-Greatest-Pose-Converter-709591348
If you Create a new morph for Daz Genesis 3 figure you may find that something happened to the teeth or naval area causing distortion. The culprit is usually the HD morphs that stayed at 100% when you originally exported a G3 .Obj to make your morph with. On my system they stay at 100% even if you zero the figure before exporting so easily overlooked.
So if you used an obj with these morphs applied, they will be there, along with your custom morph on import using morph loader.
If you don't want to do your custom morph all over again, you can zero out the teeth and navel morphs from within Daz Studio itself to clear the HD morphs.
1. With your "corrupted" morph loaded, add it to favorites by clicking the heart. The rest of this short 'how-to' assumes there are no more morphs in favorites. This is for the "teeth"
2. Go to Tool Settings>Geometry Editor, then right click and navigate to Geometry Selection>Select by>Surfaces>teeth
3. Right Click again and this time do Geometry Selection>Convert Selection>Convert to Vertex Selection
4. Right Click and do Morph Editing>Clear Selected Deltas from favorites
5. You should do this for the "mouth" too. Then, Zero your figure and make sure no morphs are applied, set resolution to zero and the Save your morph asset again.
When you reload Genesis 3 and apply your morph the problem should be solved ;-)
(For the Navel you may need to manually select the navel area and then clear the "Torso")