[Smush Pro] Issue with odd code on website

Recently, I experienced a client's website displaying odd text/code. It appears that it would only display where there's currently an image. After, disabling the CDN option within Smush Pro, the issue was resolved.

Here's the link to the screenshot, https://cl.ly/75059f41196e.

Wondering why this has happened. Would love to know if I can't use the CDN on this particular website, if not, why.