Bone setup is ok (checked it in blender). The problem surely stems from the UE lighting implementation and not from the daz model. The mesh itself bends correctly (with jcms). Even without any texture the shadow is still there. (see example)
Strangely the bones in blender look differently, esp. the offsets (collar and shoulder bend bones aren’t connected in blender), but it doesn’t seem to have any effect on the animations, but on the shading? (example 2 with a similar pose) But why do have my MakeHuman characters this problem as well?
I would have noticed any bad effect in my animations…
The question now is if it is specific to the 4.25.1 DQ version of UE or if it is a general problem, that should be reported to Epic?