When an automatic update is not successful, or any update type of update triggers a fatal error, WordPress core puts your site into schedule maintenance mode, but I don't want this behavior since am developing, and sometimes, I even trigger this error myself during update response in other to inspect the result.

CodePudding user response：

When update runs then WordPress creates a maintenance file at root. When update completes then WordPress automatically deletes that file but if fails then the file is not deleted and website will still show it is under maintenance. So you need to delete this file manually when updates.

Please let me know if it fixes the issue.