This seems to be a regression caused by MOBILE-4420. In that issue, to force unloading the previous SCO before setting the new one, we first set an empty src (empty string) and then set the final URL.

This works fine in Android, but in iOS sometimes the iframe gets stuck loading an "about:blank" page.

One possible solution would be to destroy the whole iframe when the src is empty instead of setting it to an empty src. This can cause a blink effect though. Also, this means everytime we change SCO we would need to set the iframe listeners again because the iframe element is recreated (we can do this using a setter on ViewChild).