a problem with text varbles

hi everyone,

If you create a title through text variables, the software also knows how to extract information through a certain character style. I know that if the same character style does not appear on a certain page, the title will continue the same title of the previous page.
In my document, there are pages where the title remains empty when the character style does not appear, and there are pages where the title continues.
what could be the problem?