We are using a Single Product Layout, with our Product Additional Information tables being within a HTML Block so we can use them inside an Accordion.
This works as intended, and displays the correct information across all of our products. However, when you try and use a Product Additional Information widget in a HTML Block, it will cause a Server Error 500 upon saving. It still saves and updates on the front-end, but it does still error.
This error prevents us from going back into a HTML Block with an Additional Information widget, as we get the Critical Error message.
My theory is that the editor for HTML Blocks does not use the preview product specified in Theme Settings -> Single Product.