msDS-UserPasswordExpiryTimeComputed returning "01.01.1601 01:00:00" for most users

Good Day!

I've just noticed that this command:

Get-ADUser -filter {Enabled -eq $True -and PasswordNeverExpires -eq $False} –Properties “DisplayName”, “msDS-UserPasswordExpiryTimeComputed” |
Select-Object -Property “Displayname”,@{Name=“ExpiryDate”;Expression={[datetime]::FromFileTime($_.“msDS-UserPasswordExpiryTimeComputed”)}} | CLIP

returns lines like that for most of my users:

DisplaynameExpiryDate                                                                
---------------------                                                                
FirstName Givenname01.01.1601 01:00:00  

With "most" i mean almost all of them. Only Exceptions are User with Domain- Admin rights and two (imo) random users.

Logon and such works as always.

I can't imagine what could have caused this. I've been playing around with our password-expiration-reminder script but i wouldn't know how it could be the reason.

The Attribute "pwdlastset" is fine for alle users. 

Reseting the Password over ADUC creates a "right" msDS-UserPasswordExpiryTimeComputed value.

Do you have any idea what causes this?

Thanks!