External DB Oracle Character Problems

Hi, we use Moodle 2.4.2 on MySQL UTF-8, using external DB for authentication - Oracle 10g OCI connection using NLS-LANG seting SLOVENIAN_SLOVENIA.EE8MSWIN1250.

The point is the all special slovenian characters like čšž are converted to csz for firstname and lastname (linked moodle fields and oracle fields).

I tried setting External db encoding to cp1250 and even SQL setup command to SET NAMES 'cp1250'

 but no success. Any ideas?

Thanks

Mitja