This function displays the hooks attached on a filter so you can see what's messing you up!

debugging_filters_in_wp.php

<?php
function viper_debug_filter( $filter ) {
	add_filter( $filter, function( $value ) {
		global $wp_filter;

		$filters = array();

		foreach ( (array) $wp_filter[ current_filter() ]->callbacks as $priority => $functions ) {
			foreach ( (array) $functions as $function => $args ) {
				$filters['Priority ' . $priority][] = $args;
			}
		}

		var_dump( current_filter(), $filters );

		return $value;
	} );
}

// Pass the filter name here
viper_debug_filter( 'the_content' );