Is it possible that someone you thought you had locked in earlier did not?
There have been a few people that have come into the discord asking about this over the past few years and in all of the cases so far it turns out that there was someone they thought locked in but did not.
Look for golden borders around all of the people on the tree. Also, look in the names list (found with a little silhouette icon under the evidence) or just by opening one of the dropdowns of names and you might be able to see a name in there you thought you had right but is not locked in.