Two problems I've noticed with Nicepage (using v 3.0.9):
If you're using a "Blog Posts" block and change the "read more" button to something else (such as "listen"), even though the editor shows the update, the page still retains "read more".
Designing your page using "theme colours" displays incorrect colours outside the editor. So I would use a Burgundy background for a block but when I preview it, it comes out blue. It is also using the wrong font as well. It's almost as if it's not paying attention to the theme settings.