Hello,
I have a browser tool that displays that you use CDN https://prnt.sc/1gorekg
Anyway, I’m absolutely sure that you have some kind of additional CDN or server cache because even if I switch to the parent theme I see that child theme is in use while checking your site in incognito window https://gyazo.com/f5c64c8212f55a0874f4f11e88fcfc91
That’s why you don’t have problem with the site while you are logged in (because it’s uncached version) and you have the issue because incognito displays a cached versions with out of date files or something.
So, ask your hosting provider is they have any additional cache tools for your site.
Regards