Perhaps there is an issue with the themes. Can you try activating a default WP theme, such as Twenty Twenty-One and see if you have the same issue? If so, then we know it has to do with your theme installation. At that point, I would remove the theme and attempt a re-install. Please backup your site before doing any such modification.

If that doesn’t work, perhaps there is a plugin affecting the site. In this case, consider deactivating plugins one by one to see if the issue goes away. Once it does, you’ll know that the last plugin you deactivated is the issue.

Other things to consider – make sure your theme and plugins are all up to date.

Look at your general settings to ensure that your site addresses are all consistent with what you are expecting to see as well.

Good luck out there!