Wrong syntax makes comments visible

Hello, wp-content/plugins/template-events-calendar/includes/events-shortcode.php contains these lines,

                                $output .= '<!=========Events Timeline Template ' . ECT_VERSION . '=========>';
                                $output .= '<div id="event-timeline-wrapper" class="' . esc_attr( $catCls ) . ' ' . esc_attr( $style ) . '">';
                                $output .= '<div class="cool-event-timeline">';
                                $output .= $events_html;
                                $output .= '</div></div>';
                        } elseif ( $template == 'minimal-list' ) {
                                $output .= '<!=========Events Static list Template ' . ECT_VERSION . '=========>';
                                $output .= '<div id="ect-events-minimal-list-content">';
                                $output .= '<div id="ect-minimal-list-wrp" class="ect-minimal-list-wrapper ' . esc_attr( $catCls ) . '">';
                                $output .= $events_html;
                                $output .= '</div></div>';
                        } else {
                                $output .= '<!=========Events list Template ' . ECT_VERSION . '=========>';
                                $output .= '<div id="ect-events-list-content">';
                                $output .= '<div id="list-wrp" class="ect-list-wrapper ' . esc_attr( $catCls ) . '">';
                                $output .= $events_html;
                                $output .= '</div></div>';

where the <!=========...=========> look like wrong HTML comments, which make the code visible in the page:

This only happens when the Iubenda plugin is active, I don’t know why.

I have replaced the equal signs with hyphens in the file, so the code is no longer visible in my page, online.

The page I need help with: [log in to see the link]