Remove useless identity-provider instances

I created three User federation-instances, to make failover possible:
ldap 01 is connected to ldaps://xxxxdc01.xxx:636
ldap 02 is connected to ldaps://xxxxdc02.xxx:636
ldap 03 is connected to ldaps://xxxxdc03.xxx:636
But it turned out, that does not work for failover.

One year later:
so I removed the instances ldap 02 and ldap03.
In ldap01 I configured the connection as follows (3 servers, space-separated):
ldaps://xxxxdc01.xxx:636 ldaps://xxxxdc02.xxx:636 ldaps://xxxxdc03.xxx:636

This works, however, all users that were not resolved via ldap01 in the old situation, need to configure their authenticatior with the appearing QR-code while logging in.

I did this on the test-environment, but not yet on production. So, to avoid this problem on production, what can be done?

Is it possible to force the users to ldap 01 in the postgres-database?
Or is there some other solution?

Who can help me out:?