Invisible favicon icon in mm topic

Following a previous question "how to switch to default favicon in hyperlinks", I also have topics with invisible favicons / icons.

Nick provided a fix (and thank you :)) "If you go to File > Options > Visual Effects and un-check "Show Favicons for Web links" then you will get the icon for your default browser instead of the site favicon". Obviously, the default browser icon works, but it is not the prefered option.

I am not clear on why this happens as the favicon is visible in the browser, but not reflected in the topic icon. So why does it happen in MM.

Is it a pixel size issue?

Can we have a bug fix?