I recently brought my Genesis 8 Female to blender using the Daz to Blender bridge. I was happy with the results until I tried to pose the figure. It seems the vertex maps for the "upper jaw" and center forehead are not parented correctly so when I rotate the head, they do not follow (I believe this is the root of the issue). I feel like I've looked at dozens of solutions online but I haven't been able to find something that works. I have no idea how to simply tell those vertex groups to follow the head's movement. Please help if you can.
The weight painting is probably off. To fix the teeth find the vertex group with the weight painting for the head first. The bones of the armature have vertex groups with the same name. I don't know if the teeth in your model is a separate object. In my model, it is.
Select the head object, go to Weight Paint mode and search the list of Object Data Properties > Vertex Groups for the head bone. If the head turns red, you probably found the right one. Remember the name of the vertex group. In my example, it's "spine.006".
Disclaimer: I used Rigify's metarig for a quick pose and the weight painting is very rough and done lazy. But it does the trick for the non-animated pose.
Go to Object Mode and select the teeth object (ignore this step if the teeth are in the head object.) Switch to Edit Mode, select all vertices of the upper teeth and the palate (key L may help). Assign the selected faces to the "spine.006" vertex group. Create a new one if needed. The upper teeth should be in place now.
Repeat the steps for the lower teeth if needed and assign them to the jaw vertex group ("spine.005" in the screenshot). So you can open the mouth properly.
For the glitch at the forehead, you need to check the weight painting in the vertex groups to see what's wrong there. There is probably one vertex assigned to another bone/vertex group or not completely assigned to the head vertex group.