thanks for the quick reply!

though I'm not entirely sure if I understand correctly. So it appears to be a problem with the hirarchy, but I didn't intentionally parent the bones to two other bones. I only extruded a jaw-bone from the head-bone by pressing E. Here are screenshots of the hirarchy inside poser and the bone arrangement inside blender. the weird thing is, that the mesh only breaks appart when i set the skinning method to poser unimesh, on "simple bones single skin - interoperable" it works fine...

the "bend" option in the properties is checked on all bones. the eyes are seperate spheres and only parented to the head, they're not part of the rig.