Unexpected console behaviour using '\b' characters

I have a these kind of code in my program:

std :: cout << process_prompt << std :: left << std :: setw( 40 ) <<  "Looping on tree: clust_tree.";
some_function();
std :: cout << std :: string( 52, '\b' );

The some_function() has a loop:

for( Int_t i = 0; i < n_entries; ++i ) 
{
    (some stuff...)
    if( i % 100000 == 0 )
    {
        percent_done = static_cast<float>(i) / n_entries;
        std :: cout << std :: setw( 4 ) << static_cast<int>(percent_done * 100) << "p" << std :: flush;
        std :: cout << std :: string( 5, '\b' ) << std :: flush;
    }
}

The process_prompt is just a fancy way I use to write a colored message saying "Process: ".

What I expect to happen is (each row is an update of the previous):

Process: Looping on tree: clust_tree.            0   p
Process: Looping on tree: clust_tree.            10  p
...

What actually happens:

Process: Looping on tree: clust_tree.            0   p
12  pss: Looping on tree: clust_tree.            0   p
54  pss: Looping on tree: clust_tree.            0   p

Somehow my cursor is always moved to the beginnig of the line. Can someone tell me what I am doing wrong? Thank you for the reponses!