"Get ChildItem : Cannot find path" showing path I did not supply - powershell

Question

I inherited a script that should simply move files from -source to -target. I am prompted for both, and after supplying the paths, it tells me that it cannot find the path while showing a path that I absolutely did not submit, but can't figure out how it's arriving there.
[Parameter(
Mandatory = $true,
Position = 0,
HelpMessage = "Root of the folders or share to archive"
)]
[String] $source,
[Parameter(
Mandatory = $true,
Position = 1,
HelpMessage = "Path of the folder or share of archive"
)]
[string] $target,
[Parameter(
Mandatory = $false,
Position = 3
)]
[int] $days = 30
)
# Get all the files from the source path, that are not shortcuts (*.lnk) and older than the days set
Get-ChildItem $source -Recurse |
Where-Object {!$_.psiscontainer -and ((get-date) - $_.lastwritetime).totaldays -gt $days -and $_.extension -ne ".lnk"} |
ForEach-Object {
# For each file build the destination path
$dest = $_.fullname -replace ([regex]::escape($source)), $target
# Move the files into the destination
Move-Item -Path $_.fullname -Destination $dest -ErrorAction silentlycontinue
}
The log says "Cannot find path '\\appserver\abc$\Automation\Daily\Archive\appserver\abc$\Storage' because it does not exist" - see how it starts repeating itself? \\appserver\abc$\Automation\Daily\Archive\ is the location of the script, whereas \\appserver\abc$\Storage\ is what I am entering as -source. So I have no idea why it is looking at the path to the script, then appending the source path concurrently.
EDIT: This is how I am calling the script (from a little-known finance application called APX):
SHELL PowerShell \\appserver\abc$\Automation\Daily\Archive\ArchiveFiles.ps1 -source \\appserver\abc$\Dataport\dpdata -target \\appserver\abc$\Dataport\archived -days 30

Answer 1

When your script starts, it is beginning in the directory that you are running it from, so it already in \\appserver\abc$\Automation\Daily\Archive\ and if you do not supply a UNC resource prefix such as \\ or A:\ then it will look for ChildItems from that directory down. So when you're supplying the folder path, it's appending that to its current directory and unable to find the new path.
As this would only happen if you had omitted the \\ at the beginning of your string, I would only expect your output if you had submitted appserver\abc$\Storage\ as your source. If you are sure you did supply the \\, then look more closely at whatever line of script is passing the command to this script, to see if there's a reason it's stripping the \\ off beforehand.