For starters, you should have only “Full strict” and that will work just fine in your case.
Second, the issue you have will most likely be because of DNS propagation, though the odd thing is that you said it happens intermittently and that should not be the case with propagation.
The issue itself happens because you are connecting directly to your server and not via the proxies. I’d check the machine’s configuration if you are override the domain’s address anywhere or whether you have issues with your local DNS resolver.
The site itself is properly configured and loads just fine.