What is your database encoding? Try to switch to utf8mb4
.
Alternatively, try to add one of these lines in your wp-config.php
file:
define('DB_CHARSET', 'latin1');
define('DB_COLLATE', '');
or
define('DB_CHARSET', 'utf8');
define('DB_COLLATE', '');
or
define('DB_CHARSET', 'utf8mb4');
define('DB_COLLATE', '');