UserPrincipal.Current throws COMException from one day to the next

This morning I started noticing some problems with several of my programs regarding Active Directory read operations. I noticed that all those applications (client and server) use the System.DirectoryServices.AccountManagement.UserPrincipal class for those read operations, while the programs still running correctly use System.DirectoryServices.DirectorySearcher.

So in order to norrow the problem down, I built the following, very simple console application

class Program
{
    static void Main(string[] args)
    {
        //this works great
        Console.WriteLine($"Enviroment.Username:{Environment.UserName}");

        //this works great
        PrincipalContext pcFull = new PrincipalContext(ContextType.Domain, "my.company.de", "dc=my,dc=company,dc=de");
        UserPrincipal upPrincipalContextFull = UserPrincipal.FindByIdentity(pcFull, Environment.UserName);

        //this doesn't work at all
        //Exception: “The specified directory service attribute or value does not exist”
        PrincipalContext pc = new PrincipalContext(ContextType.Domain);
        UserPrincipal upPrincipalContext = UserPrincipal.FindByIdentity(pc, Environment.UserName);

        //this doesn't either, same exception
        UserPrincipal upCurrent = UserPrincipal.Current;

        Console.ReadKey();
    }
}

As you can see in the comments, the two latter operations will fail on every Computer in the domain i tested it on, even though they worked perfecly for several years. The following Exception occures when I call UserPrincipal.Currentor UserPrincipal.FindByIdentity(pc, Environment.UserName); without specifying the Container in the PrincipalContext:

System.Runtime.InteropServices.COMException: “The specified directory service attribute or value does not exist”

Here is what I know:

• none of the applications that suddenly stopped working received an update within the last two weeks
• all of those applications, the UserPrincipal.Current-Property and the UserPrincipal.FindByIdentity-Method worked perfectly yesterday
• Workstations did not receive Windows or .Net updates in the last week
• the phenomenon does not relate to a single workstation, user or OS, but occures for a lot of different users, on a lot of different machines running Windows 7 or 10.
• Domain Controllers received updates a week ago. Apparently one of those updates has a known issue about LDAP queries: Due to a defect in WLDAP32.DLL, applications that perform LDAP referral chasing can consume too many dynamic TCP ports. It seems unlikely that this is the reason for the sudden failures because a) that patch was installed a week ago and the Problems only occured today and b) the suggested Workarounds from Microsoft (restarting Services) don't have any effect

If you have any idea what might have caused such a behavior "over night", please share it with me. If it really is related to a Windows update, other users will soon be experiencing this bug too!

I can obviously build Workarounds, so I don't have to use the failing methods and properties, but I still have to know why it stopped working in the first place.

Edit: To start with, it would be useful to understand the difference between public PrincipalContext(ContextType contextType); and public PrincipalContext(ContextType contextType, string name, string container);. The PrincipalContext constructed without container still has to obtain that container somehow, doesn't it?

Also, if you downvote my question, it would be really nice to know, why. Otherwise it's difficult to improve ;)