On my last couple trips, online checkin asked for the data anyway, despite it being in the reservations already (and me checking the box telling UA to store it).

Also, I was asked for the info on the return, despite it being provided on the outbound (and being in the reservation beforehand).

It was working better before they had the alleged functionality of storing this info in your profile (i.e., in the last round of web updates where they've introduced this and a number of other bugs).

At this point, I am going to stop entering the information until required at checkin.