Fault in external storage

I used Nextcloud normally. And I can no longer handle external storage. I proceeded to the setting and disabled the external storage app once. Then I could not access Nextcloud. HTTP Error 500. Even if I run OCC, it also does not work.

The value of enable for files_external in oc_appconfig in the MySQL database was “no”. When I changed this to “Yes”, Nextcloud was successfully restored.

Nextcloud does not work I could escape a fatal problem, but external storage became unusable.
When I look at the setting item App “external storage support” is enabled. I disable it by pressing the button and Nextcloud will stop again. That means I can not disable External Storage Support in the UI.

There are no external storage items in the setting with the application enabled.
I want to use external storage. How do I become able to use external storage?
External Storage Support apps is 1.4.1.

Nextcloud 13.0.1 / CentOS7.5 / PHP 7.1.18 / nginx 1.13.8 / MariaDB 5.6

Some users are able to connect to external storage. That user can process files. It seems that the external storage function is not completely stopped. How can I make external storage setting items display on Account>Settings? *There are no errors recorded in the Nextcloud log.

After that I tried replacing DB files.
I backed up one day ago and I restored it. Then “external storage” is displayed in the setting. When I selected it, the phrase “No external storage configured or you do not have the permission to configure them” was displayed. And it was also recorded in the log of Nextcloud. And it seems to be able to handle files on external storage.

Error core Can't get app storage, app files_external, user not logged in

Is it possible to reset by deleting all tables related to external storage with phpMyadmin? But this is scary when thinking of failure.
Where does this have a cause?