Mesh Issues on Modular Character

Hey Guys!

After i retargeted and combine my Skeletal Meshes in my Player Character, i saw some issues on the Mesh. (please look at the screenshot).

My Question is, how can i fix the connections?
In my Case, my Character has 12 Parts

  • Hair
  • Head
  • UpperBody (Torso)
  • LeftUpperArm > LeftLowerArm > LeftHand
  • RightUpperArm > RightLowerArm > RightHand
  • LowerBody (Hips)
  • LeftLeg
  • RightLeg

Any other Questions? let me Know! Thanks!!!