ADFS Server Updatepassword 407 Error

Hi fellow tech community participants,

I have an ADFS Server (Windows Server 2016) which has recently started to throw errors when trying to use https://adfs.contoso.com/adfs/portal/updatepassword to change a user password.

The user is getting a message like "user id or password is incorrect even though the username and password are correct.

In the Eventlog of the ADFS I can see a 407 Error with the following content:

Password change failed for following user:

Additional Data

User:
user@domain.com

Server on which password change was attempted:

Error details:
UserNotFound

What bothers me the most is that there seems to be no server on whicht the change was attempted.

Using nltest I get the following output:

C:\Windows\system32>nltest /DsGetDc:contoso.com /pdc
Getting DC name failed: Status = 1355 0x54b ERROR_NO_SUCH_DOMAIN

I can ping the PDC just fine and I can see that it tried using that server 3 days ago when someone entered a wrong password in the change password dialog.

Does anyone know how to resolve this?

Regards

Carste