If this customer used to belong to the other control account set, you were on the right track.

If you restore an old archive invoice or restore an old invoice from History, the old control account will be stored on the document.

If you modify the Column editor for the batch entries, you can add H - Control Acct Set to the columns displayed. If the document still has the old control account set on it, just change the customer number in the Bill to and then change it back.