powershell Command Works When run alone, but note when scripted - powershell

Question

I am working on a deployment script for some software, and my script is working on probably 90% of the machines it runs on, but on the other 10%, I get a failure in the download portion. Here is what I have:
$tls = "Tls";
$Token = "#ZorusKey#";
[System.Net.ServicePointManager]::SecurityProtocol = $tls;
$source = <Source>
$destination = "C:\installers\ZorusInstaller.exe";
$WebClient = New-Object System.Net.WebClient
$WebClient.DownloadFile($source, $destination)
I have created the C:\installers folder on all target machines, so I don't think that's the problem. When run as a script, I get the following exception:
Exception calling "DownloadFile" with "2" argument(s): "An exception occurred during a WebClient request."
At C:\Windows\system32\config\systemprofile\AppData\Local\f1e96243cb9c4ef0b0336a152ed8827f.ps1:8 char:1
+ $WebClient.DownloadFile($source, $destination)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : WebException
Which then causes the following steps to fail, as the downloaded file doesn't exist.
I have also taken the step on several of the failing machines of running each line of the script above one at a time (copied / pasted from the same Powershell ISE window) and the download works without issue. looking for a possible reason / resolution.
Thanks in advance.