Opera Portable 12.17 forgets language settings

When I run Opera Portable for first time, UI shows in English.
If I change "User Interface language" to Spanish ("es-ES" or "es-LA"), setting is lost after restarting the browser, and UI shows in English again.
Same issue with "preferred language for Opera and webpages" setting.
Both settings are always lost after restarting Opera Portable.
All other settings are preserved.
Tested on Spanish versions of Win XP and Win 7.

Seems to be the same issue described in this old post:
https://portableapps.com/node/25188
This post mentions a "OperaPortable.ini" file ( https://portableapps.com/node/25190 ) that fixes this issue, but now is unavailable.