Query Monitor finds this error open_basedir…

My website has gone painfully slow so have been advised to install Query Monitor.

It repeatedly finds this PHP error:

Message:
is_file(): open_basedir restriction in effect. File(/en.js) is not within the allowed path(s): (/var/www/vhosts/colinwalton.co.uk/:/tmp/)

Location:
wp-includes/class-wp-editor.php:516
is_file()
wp-includes/class-wp-editor.php:516
_WP_Editors::editor_settings()
wp-includes/class-wp-editor.php:308
_WP_Editors::editor()
wp-includes/general-template.php:3812
wp_editor()
wp-admin/edit-form-advanced.php:604

I have set the Plesk open_basedir to the default setting:
{WEBSPACEROOT}{/}{:}{TMP}{/}

This would appear to be correct but no success.

Another website on the same server using identical settings does NOT have the same error messages.

Any ideas where I am going wrong?

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