Cannot clear user database error

When I run the user database check tools I get this error

Warning: 1 entries in the core_acl_aro table without corresponding users table rows.

Following entries of user_usergroup_map table are missing in users table: user id=846 (aro_id=). This core_acl_aro entry with aro_id 0 should be removed, as it's not allowed.

This one can be fixed by first backing up database then by clicking here.

The automated fix does not work. There is no user with ID 846 shown if I display all users.

Can anyone help me with a manual fix?

jan.swanwick wrote: Following entries of user_usergroup_map table are missing in users table: user id=846 (aro_id=). This core_acl_aro entry with aro_id 0 should be removed, as it's not allowed.

Do a user sync first and then run the tools again.

Hi

I should have said that has been done first. All the tools run OK, except the user database check.