Get "ORA-29275: partial multibyte character" error when querying table with encrypted data. (4327242)

When running a query on a table containing some encrypted unicode data, through Toad for Oracle, and other columns containing English text or encrypted data stored in a VARCHAR2 column, Toad for Oracle throws error "ORA-29275: partial multibyte character".

It is found that the SQL*Plus 11g displays the query without getting ORA-29275 error at all, however the unicode text is garbled.

Environment : Oracle database server and Oracle database client are both Oracle 11g