Issues with accented characters using server=POOLED in file the tnsnames.ora

I have an ORACLE database on Amazon RDS that uses the connection method server=POOLED.
I am experiencing issues with accented characters.
I am executing the following commands in the user's session:

ALTER SESSION SET NLS_TERRITORY=BRAZIL;

ALTER SESSION SET NLS_LANGUAGE='BRAZILIAN PORTUGUESE';

And on the OS, I am executing:

export NLS_LANG=PORTUGUESE_BRAZIL.AL32UTF8

I only encounter issues when the tnsnames file has (SERVER = pooled). When it is set to (SERVER = dedicated), the problem does not occur.

Engine version
21.0.0.0.ru-2024-01.rur-2024-01.r1
BANNER_FULL

Oracle Database 21c Standard Edition 2 Release 21.0.0.0.0 - Production
Version 21.13.0.0.0