Please deactivate all other plugins and reactivate them one by one and check if the issue exists until you figure out the problematic plugin (in most cases its caused by a poorly coded plugin causing errors in the backend).
It has recently came to notice that the following plugin is causing issue for a couple of users (https://wordpress.org/plugins/page-links-to/). If you find the problematic plugin do update me so that I can try to make it compatible.
Thank you so much
As you told me, the problem is in the plugin “Page Links To”.
The problem has been resolved.
Compatibility update released to address this specific plugin.
Yes the update has been completed and the problem has completely disappeared.
Thank you for your efforts
