Compatibility Issue with WP 5.8?

[nick6352683]

I have a site with WP 5.7.2, and everything is perfect...

However, on a site with WP 5.8 installed, the button works, and redirects me to the Theme Customizer, but once I try to make any changes to any of the settings, I am getting a message that the session is expired and is giving me the login screen (inside the customizer's preview screen). Once I log in, all is good again, I can make the changes, and I cannot save the changes (as this is what we want), and the "Back To Demo" button works as well, negating all the changes I make in the customizer settings.

Thanks.