Prepared statement setting wouldn't effect the character display.
Character displays depend on three areas being in sync. The charset in the database column, the charset in the connection file, and the charset on the page itself in the html. If they don't match, then you can have character encoding issues. Make sure you have the charset correctly set in all 3 places.
I'd try changing the encoding back to the original value in the database. The utf8mb3 could be the issue.
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