Thanks for writing in!
I’d recommend that you clear your caching plugin, and disable it during development. This can cause Customizer changes to not take place on the front end. It will eventually show up when the cache regenerates, but it’s not ideal if you’re looking to see your changes immediately. Caching plugins are best to turn on only when you’ve finished building the site.
Moreover, keep disabling the plugins one by one until you detect that which of the plugin causes the glitch.