How can I avoid that my object deforms itself while rotating?

When I rotate an Object which is in a hierarchy of another Object it deforms itself how can i avoid it? It gets very annoying.

hi;
that’s so annoying ;
i saw this before when i got a rigged body or 3d object i downloaded from the web ;

so if this happens inside unity it should be a parent child problem;

pls send some screen shot from the editor ;;