I am very sorry if this has been questioned here before.
How to disable Atahualpa Page Options and its correspondent custom fields?
I am using qtranslate plugin and it seems there is slight conflict with atahualpha page options.
I have to manually delete the custom field's value first to have the title updated.
Otherwise this kind of title will be displayed.
<--:ID-->Peluru vs Plat Baja (1)<!--:--><!--:en-->A Bullet Hitting Steel Plates (1)<!--:-->
Thank you very much for your help.