Contradictory values from Active Directory regarding password expiry date

I am using Powershell to determine the password expiry date for domain accounts. I have used the following command to get this information:

Get-ADUser -Filter {SamAccountName -eq "<username>"} -Properties "DisplayName" , "msDS-UserPasswordExpiryTimeComputed"

I then covert this value to a meaningful date by using:

[datetime]::FromFileTime(<computed filetime from above command>)

This works fine for all the domains I use, except one. In that domain I get a value of 9223372036854775807 as the msDS-UserPasswordExpiryTimeComputed. I am not able to use the FromFileTime function to convert this number into a date. It throws as error. Upon researching I have found that this number means that the password is set not to expire. However, I know that passwords do expire in this domain. Further, the PasswordNeverExpires property from the Get-ADUser cmdlet shows as False.

How can I get 9223372036854775807 from msDS-UserPasswordExpiryTimeComputed attribute and get a False from the PasswordNeverExpires property? This seems like a contradiction. What am I missing? Are there other situations when msDS-UserPasswordExpiryTimeComputed could be 9223372036854775807 too? Thanks.

The documentation lists several conditions in which msDS-UserPasswordExpiryTimeComputed returns 9223372036854775807 aka 0x7fffffffffffffff aka [int64]::MaxValue (TO refers to a given target object):

If any of the ADS_UF_SMARTCARD_REQUIRED, ADS_UF_DONT_EXPIRE_PASSWD, ADS_UF_WORKSTATION_TRUST_ACCOUNT, ADS_UF_SERVER_TRUST_ACCOUNT, ADS_UF_INTERDOMAIN_TRUST_ACCOUNT bits is set in TO!userAccountControl, then TO!msDS-UserPasswordExpiryTimeComputed = 0x7FFFFFFFFFFFFFFF.
[...]
Else, if Effective-MaximumPasswordAge = 0x8000000000000000, then TO!msDS-UserPasswordExpiryTimeComputed = 0x7FFFFFFFFFFFFFFF (where Effective-MaximumPasswordAge is defined in [MS-SAMR] section 3.1.1.5).

Without knowing all the details, it seems that the msDS-UserPasswordExpiryTimeComputed property returning 0x7FFFFFFFFFFFFFFF indicates that there is effectively no password expiration, for a variety of reasons, only one of which is PasswordNeverExpires being set to $True.

Therefore, you could filter out such values:

Get-ADUser -Filter "SamAccountName -eq '<username>'" `
           -Properties DisplayName, msDS-UserPasswordExpiryTimeComputed |                    #`
  Where { $_.msDS-UserPasswordExpiryTimeComputed -ne 0x7FFFFFFFFFFFFFFF } | ForEach {
      # ...
      $dt = [datetime]::FromFileTime($_.msDS-UserPasswordExpiryTimeComputed)
    }

It may even be possible to incorporate the test for 0x7FFFFFFFFFFFFFFF into the -Filter argument.

^{As an aside: Note that I've used a string rather than a script block ({ ... }) as the -Filter argument, because using script blocks is best avoided.}