I did speak to EtihadHelp, the responses are not good either but I did manage to get someone to say they will forward the bug report to the correct department. However, that does not seem to have fixed it.

Anyhow, I successfully boarded my flight and the check-in agent filled in my passport details for me.

But I am surprised that an airline as prestigious as Etihad can allow such basic issues to occur on their website and not do anything about it in a decent time frame, sometimes I struggle to even get the flight search on their website working.