I have a similar problem to another user - and I have tested on a near-empty clone of the same website with most of plugins disabled.
Since updating Cornerstone in Febuary (with the slight changes to the layout), the Theme’s options have changed and now these are very limited - just to the colours of the buttons - and that’s about it.
What has happened to all the other theme options (e.g. Header, Footer, Fonts, etc.)?