Issue with ACF and setup_postdata

On my single post template, I hook a partial template using the following code in order to display related products above the post content :

The headline value is returned correctly. However, when it comes to product, it returns values of the current post (and not the related post). As you can see setup_postdata is here, so I don’t really understand… In addition print_rreturns the correct values.

Any idea ?