Errors with Get-ChildItem trying to scan network for all .mdb files - windows

Question

I am very new to using powershell and trying to execute a script that scans the entire network for all .mdb and .accdb files, for example, and generates a spreadsheet containing the data on them that I process elsewhere.
I put the sensistive data that I didnt want to provide in ()s
Here is my code:
#single threaded
import-module activedirectory
$arr = #()
$computers = Get-ADComputer -filter 'name -like "(employee computers)*"' | Select -Exp Name
foreach ($computer in $computers) {
Write-Host "Scanning" $computer "..."
gci \\$computer\c$\* -Include *.mdb, *.accdb -Recurse | ? {$_.PSIsContainer -eq $False} | % {
$obj = New-Object PSObject
$obj | Add-Member NoteProperty Directory $_.DirectoryName
$obj | Add-Member NoteProperty Name $_.Name
$obj | Add-Member NoteProperty FullName $_.FullName
$obj | Add-Member NoteProperty Size $_.Length
$obj | Add-Member NoteProperty CreationTime $_.CreationTime
$obj | Add-Member NoteProperty LastWriteTime $_.LastWriteTime
$arr += $obj
Write-Host "Scanning..."
}}
$arr | Export-CSV -notypeinformation '(path)\EmployeeDBs.csv'
This has been working pretty well so far, but for certain machines and/or directories on some machines I am receiving the following error messages:
Get-ChildItem : The specified network name is no longer available
[Get-ChildItem], IOException
+ FullyQualifiedErrorId : DirIOError,Microsoft.PowerShell.Commands.GetChildItemCommand
and
Get-ChildItem : An object at the specified path \\(employee computer)\c$ does not exist.
[Get-ChildItem], IOException
+ FullyQualifiedErrorId : ItemDoesNotExist,Microsoft.PowerShell.Commands.GetChildItemCommand
I have been googling around but havent had much luck in understanding these error messages. Would somebody be able to explain what the issues are?
I am thinking (hoping) that they are permissions problems because I am testing the scripts on my personal machine before I run them from the admin machine
Any insight is greatly appreciated!
EDIT: below is my edited code for asynchronous execution:
import-module activedirectory
$computers = Get-ADComputer -filter 'name -like "wa-150*"' | Select -Exp Name
Get-job | Remove-Job -Force
Remove-Item -path (path)\EmployeeDBs.txt
foreach ($computer in $computers) {
$scriptBlock = {gci \\$($args[0])\c$\Users\z*\Desktop\* -Include *.mdb, *.accdb -Recurse | ? {$_.PSIsContainer -eq $False} | % {
$obj = New-Object PSObject
$obj | Add-Member NoteProperty Directory $_.DirectoryName
$obj | Add-Member NoteProperty Name $_.Name
$obj | Add-Member NoteProperty Size $_.Length
$obj | Add-Member NoteProperty CreationTime $_.CreationTime
$obj | Add-Member NoteProperty LastWriteTime $_.LastWriteTime
Write-Output -InputObject $obj
}
}
while ((Get-Job -State Running).Count -ge 20) {
Write-Host "Full - Waiting ... "
Start-Sleep -Seconds 5;
}
Start-Job -name $computer -ScriptBlock $scriptBlock -ArgumentList $computer
#Invoke-Command -ScriptBlock $scriptBlock -ArgumentList $computer
}
Get-Job | Wait-Job | Receive-Job | Out-File -Append -FilePath '(path)\EmployeeDBs.txt'
Write-Host "Done"