Content is intermittently loading not always

I have one page hosted on one of my AEM server [0] and from another AEM server [1], I am getting this page in IFRAME. Issue is sometimes [0] gets loaded in [1] and sometimes not and shows CORS origin policy error. I am not getting this, if it is related to CORS Policy configuration, then why its not occurring always?

One thing which i noticed that When Page is loaded successfully, response header looks like this:

Accept-Ranges: bytes

Connection: Keep-Alive

Content-Length: 72090

Content-Type: text/html; charset=UTF-8

Date: Tue, 16 Jul 2019 16:50:46 GMT

ETag: "1199a-58dce3e14d28a"

Keep-Alive: timeout=60, max=100000

Last-Modified: Tue, 16 Jul 2019 15:43:47 GMT

Server: Apache/2.4.29 (Red Hat) OpenSSL/1.0.2k-fips Communique/4.2.2

And when it does not get load, it looks like:

Connection: Keep-Alive

Content-Type: text/html;charset=utf-8

Date: Tue, 16 Jul 2019 16:50:30 GMT

Keep-Alive: timeout=60, max=100000

Server: Apache/2.4.29 (Red Hat) OpenSSL/1.0.2k-fips Communique/4.2.2

Transfer-Encoding: chunked

X-Content-Type-Options: nosniff

X-Frame-Options: SAMEORIGIN

[0]: https://www.cornerstones4care.com/get-real/sign-up.html

[1]: https://www.getrealaboutdiabetes.com/sign-up-for-diabetes-tips.html

You can check, in [1] there is iframe which is loading [0].

Please help.