When react unmount and remount child component if parent component updates?

Question

My code looks like

@connect((store)=>{
    return{        
        obj:store.obj
    }
})
class ParentComponent extends React.Component{ 
     render(){
            return(
                   <ChildComponent/>   
             )
      }        
}

Store change is causing re-rendering of ParentComponent which is fine. But the issue is, it's triggering componentDidMount in ChildComponent each time the ParentComponent is re-rendering. I am really not sure what I am missing here. NOTE: The issue is reproducible only in react production build. Working fine in React Dev build.