ORA-29275 partial multibyte character - How to fix it?

I have got during
select * from Table;
ORA-29275 partial multibyte character and no result.
Message:
ORA-29275 partial multibyte character
Cause: The requested read operation could not complete because a partial multibyte character was found at the end of the input. Action: Ensure that the complete multibyte character is sent from the remote server and retry the operation. Or read the partial multibyte character as RAW.


After a lot of experiments and tryings I have fixed the damaged field and record.
select TITLE from Table WHERE REC_KEY=348;
Unfortunately in the Table is more such damaged records. The DB code is UTF-8. There is an application, which enables to change field TITLE manually in given REC_KEY, but I dont know what in the field is wrong. How can I fix it? How can I fix the number of records which cause  ORA-29275 partial multibyte . How can I select is as RAW (as adviced in message, to read how?). Could you help me? Many thanks.