General error: 1366

I’m getting this error on Step #7:
 
CDbCommand failed to execute the SQL statement: SQLSTATE[HY000]: General error: 1366 Incorrect string value: ‘\xEF\xBC’ for column ‘lastname’ at row 1
 
I’ve done some sleuthing in the database and have confirmed that there are users with Cyrillic and Japanese characters in them.
Below are the lines from the debug log:
2017/02/11 22:21:30 [info] [ub_data_migration] Continue running step #7
2017/02/11 22:21:39 [info] [ub_data_migration] (Continued) migrated data in step #7 ok with 100 Sales Orders.
2017/02/11 22:21:40 [info] [ub_data_migration] Continue running step #7
2017/02/11 22:21:48 [info] [ub_data_migration] (Continued) migrated data in step #7 ok with 100 Sales Orders.
2017/02/11 22:21:48 [info] [ub_data_migration] Continue running step #7
2017/02/11 22:21:57 [error] [ub_data_migration] CDbCommand failed to execute the SQL statement: SQLSTATE[HY000]: General error: 1366 Incorrect string value: ‘\xEF\xBC’ for column ‘lastname’ at row 1
 
Additionally, I’ve investigate the database collation and confirmed that it is UTF-8 as is the table, and the column encoding on the Magento1 database.