This happens due to the fact that some of the UI elements use a WorldToScreen node which uses the position of a specific bone of the character. 


If you are using the standard UE4 skeleton everything should work out fine. If you are using a different skeleton you have to edit the variable "BoneUsedForOverlay" inside the "BPC_CombatCore" component. This also enables you to change the position of the widget, e.g. by using a different bone name like "head".