Hi there,
the HTML structure of the post has been ‘changed’.
This is either due to a Theme Template being edited or some other code interfering with the layout. Most likely injecting some broken HTML.
Code can be a plugin, a custom function or some code in a GP hook.
I suggest you disable everything apart from GP Premium, including any child themes, custom functions or code added to a Hook to see if this resolves the issue. Then work back from there.