Sorry to hear of the problem you are having.
I have tested it on my test site and it’s working fine for me using latest version of theme.
This can be due to plugin conflict on your site so please try temporary deactivating all plugins and see whether everything works fine and then enable the plugins one by one to see which plugin is conflicting if any.
Are you facing this issue with any particular Customizer field or all?
Could you please also try changing and saving the settings multiple time?