Build hangs but works after a while

 [21:28:08][Step 3/4] Attempting to perform the InitializeDefaultDrives operation on the 'FileSystem' provider failed.

It hangs on the ps1 file for a long time, then it finally throws the following error. It all goes through eventually but it never used to do this and now my builds take a long time, when they used to take a few minutes.

[Step 3/4] Attempting to perform the InitializeDefaultDrives operation on the 'FileSystem' provider failed.

I upgraded to 2017.2.2 today thinking that might help, but nothing changed.

Here's a copy of the ps.

$ftp = "ftp://xxxxxxx"
$user = "administrator"
$pass = "xxxxxxxxx"

#SET CREDENTIALS
$credentials = new-object System.Net.NetworkCredential($user, $pass)

function Get-FtpDir ($url,$credentials) {
$request = [Net.WebRequest]::Create($url)
$request.Method = [System.Net.WebRequestMethods+FTP]::ListDirectory
if ($credentials) { $request.Credentials = $credentials }
$response = $request.GetResponse()
$reader = New-Object IO.StreamReader $response.GetResponseStream()
$reader.ReadToEnd()
$reader.Close()
$response.Close()
}

function Del-File($url,$credentials) {
$request2 = [Net.WebRequest]::Create($url)
$request2.Method = [System.Net.WebRequestMethods+FTP]::DeleteFile
if ($credentials) { $request2.Credentials = $credentials }
$response2 = $request2.GetResponse()
}

function Del-Directory($url,$credentials) {
$request3 = [Net.WebRequest]::Create($url)
$request3.Method = [System.Net.WebRequestMethods+FTP]::RemoveDirectory
if ($credentials) { $request3.Credentials = $credentials }
$response3 = $request3.GetResponse()
}

function Read-And-Del($url, $credentials) {
$folderPath = $url
$Allfiles=Get-FTPDir -url $folderPath -credentials $credentials
$files = ($Allfiles -split "`r`n")

foreach ($file in $files){
if($file -ne "") {
$source=$folderPath + "/" + $file
$source

$extn = [IO.Path]::GetExtension($source)
$extn

if($extn -eq "") {
Read-And-Del -url $source -credentials $credentials
Del-Directory -url $source -credentials $credentials
} else {
Del-File -url $source -credentials $credentials
}
}
}
}

Read-And-Del -url $ftp -credentials $credentials