Error calling move_account

I have one account that I’m trying to move to another instance. I used the settings UI, and it seemed to work, but a surprisingly small percentage of followers auto-moved. (I understand the optionality, but suspected that not all followers received the Move activity.)

So, now following the logs, I have been trying again. But it fails and logs a FunctionClauseError in Pleroma.Web.ActivityPub.ActivityPub, function: : "-object_to_user_data/2-fun-1-"

I’ve poked around the database looking for obvious issues, but am not literate enough to diagnose this. Pointers will be much appreciated!