function to_char(iso-8859-1) is not unique at character 8

Hi, 

I upgraded the version of PostgreSQL from 12.6 to 12.13, 

when I execute the sql below , the to_char function caused the following error.

---------------SQL------------------

select TO_CHAR('1000000');

ERROR:  function to_char(unknown) is not unique at character 8

HINT:  Could not choose a best candidate function. You might need to add explicit type casts.

There is no problem before the upgrade and to_char function comes from the Orafce extension.

The configuration of the old and new databases is as follows.

Database server (old): PostgreSQL 12.6（orafce3.13）

Database server (new): PostgreSQL 12.13（orafce3.24）

The new database has successfully installed the orafce 3.24 extension.

It does not occur in "PostgreSQL 12.6 and orafce 3.13", 

but occurs in "PostgreSQL 12.13 and orafce 3.24", 

so either the difference between 12.6 and 12.13 or the difference between orafce 3.13 and 3.24 is suspicious.

What is the reason for the problem and how to fix the error?

Regards