I just noticed that some themes(including our DEMO theme) uses "single_post_title()" to display the page title. I've solved this in our DEMO by applying the solution below,
1. Open {root}/wp-content/plugins/another-events-calendar/includes/class-aec.php
2. Find the line,
$this->loader->add_filter( 'the_title', $plugin_public, 'the_title', 99 );
3. Add the following code below the above line,
$this->loader->add_filter( 'single_post_title', $plugin_public, 'the_title', 99 );
4. The final code should look like,
$this->loader->add_filter( 'the_title', $plugin_public, 'the_title', 99 );
$this->loader->add_filter( 'single_post_title', $plugin_public, 'the_title', 99 );
5. Save the changes and try now.
Hope, this works for you too.