WP_DEBUG must be on, otherwise edit post or page will show 404 error
encountered a very strange error: my WP_DEBUG must be on (set to true), otherwise editing post or page at the admin panel will show the 404 error. While the save post/page can still be seen.
The wordpress version is 5.6.
What might be the underlining cause of this error? Has anyone seen this before?
Thanks a lot!