WordPress doesn’t detect upgrade after latest version is installed

Hi all. I am trying to update WordPress to the latest version(4.9.1). The installation of new version of WordPress seems to be updated successfully as show in the picture. Except, my site was redirected to previous version’s (4.9) about page after installation, and from the dashboard my site still shows the information of ‘update available’. I double checked the version.php under wp-include. It shows the latest version number(4.9.1). I am wondering why my site doesn’t detect the upgrade of wordpress? Appreciate if any one can advise the problem. Thank you.

Kindly refer to the following link for all pictures.
here

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