Autocomplete rule to validate special characters in Assignment Name

Summary:

We have a requirement to restrict special characters Assignment Name

Below are the characters not allowed .

Special Characters : !@#%*?{}$|><;~`^[]

Letters : ÀÁÂÃÄÅÆBÇĆČĐEÈÉÊËĘĞÌÍÎÏİŁÑŃÒÓÔÕÖØŒSŚŞÙÚÛÜŰÝŸŽŹŻàáâãäåæçćčđèéêëęğìíîïłñńòóôõöøœśşùúûüűýÿžźż

We have build below auto complete rule and it is working fine for most of the cases. But it is failing for specific employee records who have historical special character data in their assignment name. It is not giving error on all historical data.

Can you please help me understand what could be the possible reason?

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