Sylius's defaut <title> implementation might cause issues, with the title being rendered twice.
As the plugin uses an event, we are forced to display the <title> tag within the event (to avoid the Debug comment to be printed in the title)
The following code from Sylius conflicts with the event dedi_sylius_seo_plugin.title
{% block title %}
{{ product.name }} | {{ parent() }}{% endblock %}
{% block content %}This code will result in the product's name to be printed and then the event dedi_sylius_seo_plugin.title been executed, which will load the <title HTML tag
000F office grey jeans | <!-- BEGIN EVENT | event name: "dedi_sylius_seo_plugin.title" -->
<!-- BEGIN BLOCK | event name: "dedi_sylius_seo_plugin.title", block name: "dedi_seo_title", template: "@DediSyliusSEOPlugin/Shop/Header/_title.html.twig", priority: 0 -->
<title>Women | 000F office grey jeans</title>
<!-- END BLOCK | event name: "dedi_sylius_seo_plugin.title", block name: "dedi_seo_title" -->
<!-- END EVENT | event name: "dedi_sylius_seo_plugin.title" -->The workaround for this is to override any template from Sylius that implements the block title like the exemple shown below
{% extends '@!SyliusShop/Product/show.html.twig' %}
{% block title %}
{{ sylius_template_event('dedi_sylius_seo_plugin.title', { resource: product ?? sylius.channel }) }}
{% endblock %}