plugin development – Cannot modify header information – headers already sent by (output started at ../misc.php:1281) in ..wordpresswp-includespluggable.php on line 1329

Hello i’m developing a plugin and the wp_redirect was working well but now it’s stop and send me an error that the header have already been sent.
Little Schemas

Home page form Post file to add_content.php -> content php treat information and redirect to home page

But now i generate an error into the add_content.php and does not redirect to home anymore.