When we tested the recent version of the Travel log theme, we were unable to find such issue.
In most cases, you can solve issues with the theme customizer by disabling your plugins in the WordPress dashboard. You could try deactivating your plugins one by one to identify the plugin that is causing the issue
Also, make sure you have the updated version of the WordPress. Finally, you could also try reinstalling the fresh theme.
Even after following all these steps you could solve the issue then kindly get back to us.