Hi,
I know it sounds general, but note 819829 is the perfect answer.
Also check the permissions of instant_client. Maybe check with other systems and look for any deviations.
Since BR*Tools working perfectly with ora<sid> (and this user is the owner of instant_client directory and files) it must be a permission issue.
Try do decompress the instantclient to another directory and check the default permissions.
Regards,
János