Steps to reproduce the issue

1 create a category blog menu
2 create an article and put in on the category blog menu made in step 1
3 set article global options->shared->Date for Ordering to Modified
4 goto frontend of site, select category blog menu made in step 1 then select article made in step 2

Expected result

Article can be viewed ok

Actual result

ERROR 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'THEN a.created ELSE a.modified END DESC' at line 5

System information (as much as possible)

Joomla_4.0.0-beta6-dev-Development-Full_Package.zip 2020-12-29

Additional comments

The error is coming from Content - Page Navigation plugin.