CDN issue

Hello I noticed that full images are correctly loaded from CDN. Thumbnails are not.
This is the code:

<a href="https://cdn.example.com/wp-content/uploads/img.jpg" itemprop="contentUrl" data-size="1920x1280" data-caption="" >
<img src=https://www.example.com/wp-content/uploads/img-192x128.jpg itemprop="thumbnail" alt=""  />
</a>

Correct code should be:

<a href="https://cdn.example.com/wp-content/uploads/img.jpg" itemprop="contentUrl" data-size="1920x1280" data-caption="" >
<img src=https://cdn.example.com/wp-content/uploads/img-192x128.jpg itemprop="thumbnail" alt=""  />
</a>

How can we fix this?