Probably the problem is related to some permission of your server because we found that we can’t even open the ThemeOptions in customizer because get 403 page. We use Kirki plugin to implement theme options for our theme and bg field of this plugin is the reason of the 403 page. We created the request to plugin author about this problem https://github.com/aristath/kirki/issues/2256 , waiting for his answer.
Sorry for this inconvenience. Looks it’s some conflict between Kirki framework and server permissions.
