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

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:

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


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!