WordPress RSS feed template with custom wp_query

I have written my own rss template with WP_Query, but it doesn’t work as intended. Here is the code:

<?php
header('Content-Type: ' . feed_content_type('rss-http') . '; charset=' . get_option('blog_charset'), true);
$more = 1;

echo '<?xml version="1.0" encoding="' . get_option('blog_charset') . '"?' . '>';

/**
 * Fires between the xml and rss tags in a feed.
 *
 * @since 4.0.0
 *
 * @param string $context Type of feed. Possible values include 'rss2', 'rss2-comments',
 *                        'rdf', 'atom', and 'atom-comments'.
 */
do_action('rss_tag_pre', 'rss2');
?>
<rss version="2.0"
     xmlns:content="http://purl.org/rss/1.0/modules/content/"
     xmlns:wfw="http://wellformedweb.org/CommentAPI/"
     xmlns:dc="http://purl.org/dc/elements/1.1/"
     xmlns:atom="http://www.w3.org/2005/Atom"
     xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
     xmlns:slash="http://purl.org/rss/1.0/modules/slash/"
    <?php
    /**
     * Fires at the end of the RSS root to add namespaces.
     *
     * @since 2.0.0
     */
    do_action('rss2_ns');
    ?>
    >

    <channel>
        <title><?php bloginfo_rss('name');
            wp_title_rss(); ?></title>
        <atom:link href="<?php self_link(); ?>" rel="self" type="application/rss+xml"/>
        <link><?php bloginfo_rss('url') ?></link>
        <description><?php bloginfo_rss("description") ?></description>
        <lastBuildDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_lastpostmodified('GMT'), false); ?></lastBuildDate>
        <language><?php bloginfo_rss('language'); ?></language>
        <sy:updatePeriod><?php
            $duration = 'hourly';

            /**
             * Filter how often to update the RSS feed.
             *
             * @since 2.1.0
             *
             * @param string $duration The update period. Accepts 'hourly', 'daily', 'weekly', 'monthly',
             *                         'yearly'. Default 'hourly'.
             */
            echo apply_filters('rss_update_period', $duration);
            ?></sy:updatePeriod>
        <sy:updateFrequency><?php
            $frequency = '1';

            /**
             * Filter the RSS update frequency.
             *
             * @since 2.1.0
             *
             * @param string $frequency An integer passed as a string representing the frequency
             *                          of RSS updates within the update period. Default '1'.
             */
            echo apply_filters('rss_update_frequency', $frequency);
            ?></sy:updateFrequency>
        <?php
        /**
         * Fires at the end of the RSS2 Feed Header.
         *
         * @since 2.0.0
         */
        do_action('rss2_head');

        $query_args = array(
            'post_type' => 'post',
            'order' => 'DESC',
            'orderby' => 'date',
            'meta_query' => array(
                'relation' => 'OR',
                array(
                    'key' => 'votes',
                    'value' => '10',
                    'compare' => '>=',
                    'type' => 'NUMERIC',
                ),
                array(
                    'key' => 'author_role',
                    'value' => array('administrator', 'contributor', 'editor', 'author'),
                    'compare' => 'IN',
                ),
            ),
            'post_status' => 'publish'
        );

        $query = new WP_Query($query_args);

        if ($query->have_posts()) :
            while ($query->have_posts()) :
                $query->the_post();
                ?>
                <item>
                    <title><?php the_title_rss() ?></title>
                    <link><?php the_permalink_rss() ?></link>
                    <comments><?php comments_link_feed(); ?></comments>
                    <pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_post_time('Y-m-d H:i:s', true), false); ?></pubDate>
                    <dc:creator><![CDATA[<?php the_author() ?>]]></dc:creator>
                    <?php the_category_rss('rss2') ?>

                    <guid isPermaLink="false"><?php the_guid(); ?></guid>
                    <?php if (get_option('rss_use_excerpt')) : ?>
                        <description><![CDATA[<?php the_excerpt_rss(); ?>]]></description>
                    <?php else : ?>
                        <description><![CDATA[<?php the_excerpt_rss(); ?>]]></description>
                        <?php $content = get_the_content_feed('rss2'); ?>
                        <?php if (strlen($content) > 0) : ?>
                            <content:encoded><![CDATA[<?php echo $content; ?>]]></content:encoded>
                        <?php else : ?>
                            <content:encoded><![CDATA[<?php the_excerpt_rss(); ?>]]></content:encoded>
                        <?php endif; ?>
                    <?php endif; ?>
                    <wfw:commentRss><?php echo esc_url(get_post_comments_feed_link(null, 'rss2')); ?></wfw:commentRss>
                    <slash:comments><?php echo get_comments_number(); ?></slash:comments>
                    <?php rss_enclosure(); ?>
                    <?php
                    /**
                     * Fires at the end of each RSS2 feed item.
                     *
                     * @since 2.0.0
                     */
                    do_action('rss2_item');
                    ?>
                </item>
            <?php endwhile; ?>
        <?php endif; ?>
        <?php wp_reset_postdata(); ?>
        <?php wp_reset_query(); ?>
    </channel>
</rss>

Everything works fine, but I get random content for each post (get_the_content_feed('rss2'); function returns random content). How can I fix this?