Hey Arunsatori,
this is indeed a bug, thank you for reporting – it seems that one of the theme scripts is interfering with the newer version of the Customizer. I’ve prepared a fix – please download this archive, unzip it, and upload the resulting file into the following folder inside your WordPress directory (via an FTP client or your hosting provider’s file manager): /wp-content/themes/Kanso/
When prompted if you wish to replace the existing file, say “Yes”. Let me know if the fix works for you!
Sincerely,
Andrii / Satori Studio