The page's title is no more removable through update engine

Creating a new page in 4 language (en, fr, de, it) by only putting a title in FR and EN. Trying to update the page by removing the FR title : in update popup engine remove the title in FR and click on apply, after the refresh of the UI , my onld title is still there, as a matter of fact we have no way to remove a title of a page...