Over the years I've had enough hassle with LH metal on 016 tickets that I just avoid it. It used to be a better deal for collecting miles but miles are so devalued now. The worst was the time I bought the ticket, used the LH PNR to get a seat online, was offered instant upgrade for a decent price, took it, only to find out 6 weeks later when I tried to check in the day before that I simply had not reservation any more at all. I have not flown them since Covid but before that LH did have good real human agents who were able to get me fixed on that flight, though no upgrade (and that took a couple of months to get reimbursed). Then when I returned to the US there were issues (as in "Do you have two passports") with a resulting wait in the penalty box along with the folks getting busted for drugs, etc. - all suggesting that the fixed reservation skipped some behind the scenes step.

Anyway, give LH (not UA) a call.