Cannot post message to child when child changes to second cross domain page

[glengiancola2016 (glengiancola2016@gmail.com)]

1. Parent domain = www.mydomain.com
2. Open child to crossdomain1.mydomain.com
3. postMessage works from parent to child.
4. Then change child to crossdomain2.mydomain.com
5. postMessage from parent to child fails or reference is lost.