The format of the recovery password provided is invalid

I am automating the installation of BitLocker.
As part of this task, a Recovery Password is being added.
Instead of using the auto-generated password I want to provide my own password.
However, not all password combinations seem to be valid.

This command line fails

Add-BitLockerKeyProtector -MountPoint D -RecoveryPasswordProtector -RecoveryPassword '123456-123456-123456-123456-123456-123456-123456-123456'

while this command line works fine

Add-BitLockerKeyProtector -MountPoint D -RecoveryPasswordProtector -RecoveryPassword '531058-303050-716078-383614-460922-106975-083446-139161'

The error message I get is the following one

Add-RecoveryPasswordProtectorInternal : The format of the recovery password provided is invalid. BitLocker recovery passwords are 48 digits. Verify that the recovery password is in the correct format 
and then try again. (Exception from HRESULT: 0x80310035)
At C:\Windows\system32\WindowsPowerShell\v1.0\Modules\BitLocker\BitLocker.psm1:2052 char:31
+ ...   $Result = Add-RecoveryPasswordProtectorInternal $BitLockerVolumeInt ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], COMException
    + FullyQualifiedErrorId : System.Runtime.InteropServices.COMException,Add-RecoveryPasswordProtectorInternal

Does anybody know what makes such a password valid?

Don’t search anymore, someone found the answer on another forum and can be found here: