Unexpected empty space using flexbox

Question

I\'ve reduced the problem to the minimum possible where the issue is still present.

I don\'t understand where the orange space is coming from.

Answer 1

I had similar problem in React Material-UI library. I got huge empty space below the TableContainer in this code:

                    
    
        
                
                    //some cells
                
            
                    //some rows
            
    

   //here I got huge empty unexpected space

Then I add container keyword in Grid and empty space disappeared.

                    
    
        
            //the same code