Object not being added to parent object in different runspace (Winforms/Powershell)

I have a function "Get-UserFolders" that I imported into the runspace using:

$Definition = Get-Content function:\Get-UsersFolders -ErrorAction Stop
$SessionStateFunction = New-Object System.Management.Automation.Runspaces.SessionStateFunctionEntry -ArgumentList 'Get-UsersFolders', $Definition
$InitialSessionState.Commands.add($SessionStateFunction)

Here is the function:

function Get-UsersFolders($ComputerName) {
    #If there is any checkboxes present, delete them
    $Indexes = @()
    Foreach ($control in $hash.sourceTab.Controls) {
        if ($control.GetType().ToString() -eq "System.Windows.Forms.CheckBox") {
            $Indexes += $control.TabIndex
        }
    }
    Foreach ($index in $indexes | Sort-Object -Descending) {
        $hash.sourceTab.Controls.RemoveAt($index)
    }


    if ($null -ne $ComputerName) {
        $global:UserFolders = Invoke-Command -ComputerName $ComputerName -Credential $script:hash.credentials -ScriptBlock {
            $array = @()
            $users = Get-ChildItem -path "C:\users" | Where-Object { $_.Name -match "^\d{6}$" }
            Foreach ($folder in $users) {
                $array += [PSCUSTOMOBJECT]@{
                    Name = "$($folder.Name)" 
                    Size = "$( [Math]::Round(((Get-ChildItem $folder.fullname -Recurse -ErrorAction SilentlyContinue | Measure-Object -Sum Length -ErrorAction SilentlyContinue).Sum / 1GB),2) ) GB"
                }
            }
            Return $array
        }
    }
    else {
        $global:UserFolders = @()
        $users = Get-ChildItem -path "C:\users" | Where-Object { $_.Name -match "^\d{6}$" }
        Foreach ($folder in $users) {
            $global:UserFolders += [PSCUSTOMOBJECT]@{
                Name = "$($folder.Name)" 
                Size = "$( [Math]::Round(((Get-ChildItem $folder.fullname -Recurse -ErrorAction SilentlyContinue | Measure-Object -Sum Length -ErrorAction SilentlyContinue).Sum / 1GB),2) ) GB"
            }
        }
    }
    
    $xPos = 0
    $yPos = 0
    $numUsers = 0
    Foreach ($user in $global:UserFolders | Sort-Object -Property Size -Descending) {
        $hash.userCB = New-Object System.Windows.Forms.CheckBox
        $hash.userCB.Name = $user.Name
        $CBLx = 10 + $xPos
        $CBLy = 10 + $yPos
        $hash.userCB.Location = New-Object System.Drawing.Point($CBLx, $CBLy)
        $hash.userCB.AutoSize = $true
        $hash.userCB.Text = "$($user.Name) - ($($user.Size))"
        $hash.userCB.Tag = "$($user.Size.split(" ")[0])"
        $hash.userCB.Add_CheckStateChanged({
                Get-PrecheckTotal
                if ($null -ne $global:driveInfo) {
                    $hash.sizeAfterLabel.text = "Space After: $([Math]::Round($global:driveInfo.Free / 1GB,2) - $global:precheckTotal) GB"
                }
            })
        $numUsers++
        $yPos = $yPos + 30
        if (($numUsers % 9 -eq 0) -and ($numUsers -ne 0)) {
            $xPos = $xPos + 150
            $yPos = 0
        }
        $hash.sourceTab.Controls.Add($hash.userCB)
        Write-host "Added Checkbox for $($hash.userCB.Name)"
    }
    Get-PrecheckTotal
}

When the function runs, it outputs to the console that the checkboxes where added to the form. I have the command:

foreach ($control in $hash.sourceTab.Controls) {
     Write-host $control
}

Which lists the controls in the form. The checkboxes are not part of this list or displayed on the form. I cannot figure out why.

Potentially helpful background: stackoverflow.com/q/6184/45375. Potential PowerShell solution (I'd personally avoid runspaces): stackoverflow.com/a/60229906/45375

Thank you mklement0