Multiple tables don’t display correctly in admin

I have four tables in a post. These display perfectly on the site:
https://www.deculinairewerkplaats.nl/pages/mee-werken/meewerk-rooster/

However, in the admin page they display side by side and all squashed up instead of underneath each other.

This makes them almost impossible to edit in the Visual tab. Does anyone know how to resolve this.

There’s a screenshot of how they look in WordPress admin here:
https://www.flickr.com/photos/amsterdame/2949671688/

Any advice much appreciated.

Thanks