Cannot modify header information - headers already sent during plugin activation

Question

I am getting this error

PHP Warning: Cannot modify header information - headers already sent by (output started at /home/zk2ba8xn663w/public_html/wp-includes/formatting.php:5100) in /home/zk2ba8xn663w/public_html/wp-includes/pluggable.php on line 1219

The error message only shows up if i am activating from TGM plugin actiavtion page, ... if i first install through tgm and then go to actual plugin activation page redirect works with out any problem.

this is the redirect i am using

function activation_redirect( $plugin ) {
if( $plugin == plugin_basename( FILE ) ) {
exit( wp_redirect( admin_url( 'admin.php?page=general-settings' ) ) );
}
}
add_action( 'activated_plugin', 'activation_redirect' );

Answer 1

Since the standard redirection works, I figured the conflict must be with TGM plugin activation already hooking to activated_plugin and producing output and thus preventing the redirect...

Therefore the solution was to ensure that the plugin activation function hook was added to an earlier priority than the (silent) default of 10 most probably used by TGM:

add_action( 'activated_plugin', 'activation_redirect', 9 );