hi, I am having a similar issue where my front page is not syncing to what I set it to in the customiser, and is instead completely white.
My page that I want to set it to is https://charleyray.co.uk/home/, a custom maintenance page.
To get around this, I've temporarily added the same copy as an intro in the customiser setting, as this is the only way I can get it to show up. However it's not a long-term solution as I want to include hyperlinks in the copy.
Have disabled all plugins, updated the theme, etc..