The last thing we can try is:
Move the buddypress.php from page templates folder to theme root directory and edit the parent functions.php to reflect the changes like below. I think buddypress will look for buddypress.php in theme root directory only.
if ( is_page_template( 'page-templates/full-width.php' ) || is_page_template( 'buddypress.php' ) || is_attachment() || ! is_active_sidebar( 'themonic-sidebar' ) ) {