I've never heard of a title being checked against a passport - moreso the gender should be correct. Titles are generally considered customary, not required. It's not actually a part of your legal name.
Do you think the machine readable portion of his/her passport has that? Does yours have "í"? Does the website not state that's what should be followed? They've already stated they've been travelling for a long time. I'm surprised they've not been subjected to multiple ID checks when flying, if they've been doing the "o" and not "oe" for flights for some time, and clearly should be aware.
Did you write it as in the machine read line at the bottom of your passport? That's the way most systems match it. (No ö anymore, but other characters, and this is the advice we've been given.)