ORA-64451: Conversion of special character to escaped character failed

Question

I am concatenating some texts and I get this weird error that I can't find anything about

UPDATE Table1 a
SET a.AllTexts = a.Text
  || a.Title
  ||
  (SELECT XMLAGG(XMLELEMENT(E,"Text",',').EXTRACT('//text()')).GetClobVal()
  FROM Table2 b
  WHERE b.El_Id = a.Id
  )

AllTexts is CLOB, all other columns are VARCHAR2

I get

Error report -
SQL Error: ORA-64451: Conversion of special character to escaped character failed.
64451. 00000 -  "Conversion of special character to escaped character failed."
*Document: NO
*Cause:    An attempt to convert a special character to an escaped character failed.
*Action:   Remove the special character that cannot be escaped.

Edit: the error is caused by some weird symbols. Problem is there is no way to know ahead which symbols will block execution

Answer 1

I got this error code and this work for me

REGEXP_REPLACE(COLUMN, '[^[:print:]]', '')