Button Color after Update

Hello,

I have changed the button color in the Theme Options of the evolve lite theme. After Updating to version 3.6.4 the button colors are changed back to the default green. I have also imported the old settings into the theme options and there the button color is set to white as required, but not displayed as selected on the website.

I am using a child theme for some other adaptions.
I have rolled back to the old theme version to have required button colors. (http://www.skulpturmanufaktur.de)

Any ideas what could cause this issue?

Thank you very much in advance.
Karl