Error

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b @ GMj00YJBc22.js?_nc_x=Ij3Wp8lg5Kz:51

The resource https://pagead2.googlesyndication.com/pagead/js/r20190826/r20190131/show_ads_impl.js was preloaded using link preload but not used within a few seconds from the window's load event. Please make sure it has an appropriate as value and it is preloaded intentionally.

Do you have any Google related code added to your site?

Like Google Adsense? In Hooks Elements maybe?

I don't understand the question well, I'm not sure. But I do have AdSense ads

Can you temporarily disable the Adsense code to see if it fixes the issue?

Removing the ads fixes the problem, but that is not a good solution for me

Strange - Adsense by themselves shouldn't break the Customizer (lots of our users use them together successfully).

I looked into that error, and I don't think it would break the Customizer. Did you remove any other code from the site when you removed it?

One alternative is to install an Ad Blocker, but it would be better to figure out why those errors are happening. Do they appear in your Console on the front-end of the site as well?