I'd rather they didn't...
I'm not sure you have any comeback if they won't ticket a flight for you that you think should be allowed.
At the end of the day the people in ticketing are human beings and will have their own KPIs and personal agendas.
So it's not a surprise that results vary on what is a complex area.
We are trying to help maximise the chances.
The OP hasn't been back to clarify what the real purpose of their journey is, so there's nothing really to suggest other than to sympathise and say that this routing might have worked in 2018.