Oxygen 4.0.2 corrects a number of important issues that we became aware of after Oxygen 4.0 was released. You should resign shortcodes and regenerate your CSS cache after updating to Oxygen 4.0.2 RC 1 and Oxygen Gutenberg 1.4.3 RC 1.
Oxygen Gutenberg 1.4.3 RC 1 contains one minor change to ensure better compatibility with Oxygen 4.x.
Existing users can download Oxygen 4.0.2 RC 1 and Oxygen Gutenberg 1.4.3 RC 1 in the customer portal.
Before using a release candidate in a production environment, backup your site. While release candidates have been tested extensively and are considered stable enough for production environments, you should always proceed with caution when using any alpha, beta, or RC version of Oxygen or the associated add-ons. We will provide official support for sites running release candidate versions of Oxygen and the associated add-ons. If you encounter bugs, please report them on GitHub.
The following is a mostly complete changelog of the changes included in Oxygen 4.0.2 RC 1.