If you go to the CMS's pages module and try creating a page manually via the admin, you can successfully change its title. But if you create a page using your store theme and try changing its title via theme or via admin, it will not be possible.

Create a new page on your theme, and try changing your title. In my example, I added the word "tema":

Go to the pages module and check if the title changed, you will see that we received the change, but it is not displayed on the title above:

The same is on the page's list:

If you try changing the title directly on the admin the result will be the same.

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