Ftp uploading failed after every two or three succeeded uploads - powershell

Question

I got the the following error message when uploading. The Powershell create a zip file using 7za.exe and call my FTP function to upload the file. What may cause the problem? Will Windows ftp.exe client be more stable?
Exception calling "GetRequestStream" with "0" argument(s): "The remote
server returned an error: (550) File unavailable (e.g., file not
found, no access)."
Update:
It seems the same files always failed in the loop. However, It works if I just run ftpFile file_name_with_full_path. (The file_name_with_full_path is copied from the output of the loop script.
Update 2:
I tried to use webclient ($webclient.UploadFile($uri, $File)) to ftp the files. Same error.
Update 3:
Found this Question. May need to add $ftp.KeepAlive = false. Why?
function ftpFile
{
Param (
[Parameter(Mandatory=$true, ValueFromPipeline=$true)]
[ValidateScript({Test-Path $_})]
[String]
$filePath
,
[Parameter(Mandatory=$false)]
[String]
$ftpUrl = "ftp://10.0.1.1/Data/"
,
[Parameter(Mandatory=$false)]
[String]
$Login = "username"
,
[Parameter(Mandatory=$false)]
[String]
$password = "password"
)
Process {
try {
$ftp = [System.Net.FtpWebRequest]::Create("$ftpUrl/$(Split-Path $filePath -Leaf)")
$ftp = [System.Net.FtpWebRequest]$ftp
$ftp.Method = [System.Net.WebRequestMethods+Ftp]::UploadFile
$ftp.Credentials = new-object System.Net.NetworkCredential("$Login","$password")
$ftp.UseBinary = $true
$ftp.UsePassive = $true
# read in the file to upload as a byte array
$content = gc -en byte $filePath
$ftp.ContentLength = $content.Length
# get the request stream, and write the bytes into it
$rs = $ftp.GetRequestStream()
$rs.Write($content, 0, $content.Length)
$rs.Close()
$rs.Dispose()
echo "ftpFile: $filePath size: $($content.Length)"
}
catch {
throw "FTP: $_"
}
}
}

Answer 1

FTP Error 550 is Access Denied and tends to be a username/password conflict.
If you're using a loop and passing the same username and password each time this function is called
AND
it's working on some iterations of the loops and not others
THEN
you need to check the ftp auth/error logs on the server to get a grasp of why you're being denied.
As #AndyArismendi asked, does it always fail on the same file? Without more complete code and understanding of your use, this is hard to lock down to a simple solution.

Answer 2

Found this Question. Need to add $ftp.KeepAlive = false.