Title appears with A. when hovering thumbnail

I created a gallery with images that have a title, a legend, but no alt text, and no description.
When the cursor hovers a thumbnail the legend text appears in a tooltip but the caracters are HTML encoded so it is quite ugly, example :
Le sourcier Pé&

The tooltip displays the title attribute of the <a> tag, so the question is :
Why does the title attribute contain an HTML-encoded-version of the legend of my media ?
Which setting can be modified to prevent this tootltip on hover ?

I have hundreds of images so I’f like to avoid modifying them one by one !
Thanks in advance for any help

HTML code of a thumbnail linked to a bigger image :

<a
    href="https://example.com/wp-content/uploads/2026/04/my-image.jpg" title="&amp;#76;&amp;#101;&amp;#32;&amp;#115;&amp;#111;..."
    data-rl_title="my-image" class="rl-gallery-link" data-rl_caption="media legend" 
    data-rel="lightbox-gallery-3"><img loading="lazy" decoding="async" 
    src="https://example.com/wp-content/uploads/2026/04/my-image-150x150.jpg" width="150" height="150" 
    alt="&amp;#76;&amp;#70;...(short version)">
    <span class="rl-gallery-caption">
        <span class="rl-gallery-item-caption">My Image</span>
    </span>
</a>