ERROR New-ADUser :The supplied user buffer is not valid - windows

Question

I made a PowerShell script to create Active Directory users from a CSV file. For one specific user I get this error
As you can see, the user has been successfully created though. All other users have been made as well. Does anyone know what this error means?
Script:
Import-Module ActiveDirectory
$csv_file = Read-Host -Prompt "Path naar CSV bestand?"
$pwd = Read-Host -Prompt "Password for users?" -AsSecureString
$csv_file = $csv_file.Replace('"','')
$csv_list = Import-Csv $csv_file
$domainname = Get-ADDomain
$domainname = $domainname.DNSRoot
$server = hostname
$usernames = (get-aduser -Filter *).name
$i = 0
foreach ($adUser in $csv_list) {
$department = $adUser.Department
if ($adUser.GivenName) {
$givenname = $adUser.GivenName
}
else {
$givenname = $adUser.FirstName
}
if ($adUser.Surname) {
$surname = $adUser.Surname
}
else {
$surname = $adUser.LastName
}
$username = ("${givenname}.${surname}" -replace (' ','')).ToLower()
if ($username -in $usernames -eq $true) {
$number = 1
}
$variableusername = $username
while ($variableusername -in $usernames -eq $true) {
$number += 1
$variableusername = [string]($username + $number)
}
$username = $variableusername
$usernames += $username
$sam = $username
if ($sam.Length -gt 20) {
$sam = $sam.Substring(0,20)
}
$path = (Get-ADOrganizationalUnit -Filter * | Where-Object -Property Name -eq $department).DistinguishedName | Select-Object -First 1
if ($path -eq $False) {
$department = Read-Host -Prompt "Could not find an OU for user $username in department ${department}. Please specify the correct OU"
$path = (Get-ADOrganizationalUnit -Filter * | Where-Object -Property Name -eq $department).DistinguishedName | Select-Object -First 1
}
$password = $pwd
$email = "${username}#${domainname}"
$title = $adUser.Title
$dpn = "${givenname} ${surname}"
New-ADUser -name $username -path $path -UserPrincipalName "${username}#${domainname}" -GivenName $givenname -Surname $surname -Department $department -AccountPassword $password -EmailAddress $email -ChangePasswordAtLogon $False -Title $title -Enabled $True -Server $server -DisplayName $dpn -SamAccountName $sam
Add-ADGroupMember -Identity "G_${department}" -Members $sam
$i++
Write-Progress -activity "Creating users . . ." -status "Created: $i of $($csv_list.Count)" -percentComplete (($i / $csv_list.Count) * 100)
}