I wrote code with the WPF window to synchronize files between two folders. After clicking the Run button, the code will run and monitor changes in folder f1. If a change is detected, it will execute the condition with f2. However, after I pressed the run button, nothing happened, WPF froze and had to be turned off. Please tell me what I did wrong and how I should fix it? Sincerely thank you!

function StartWatching {
    param (
        [string]$F1s,
        [string]$F2s,
        [bool]$Recycles,
        [bool]$Backups,
        [string]$BackupPaths,
        [int]$Time
    )

    if (($Recycles -eq $true) -or ($Backups -eq $true)) {
        Check-Folders -F1 $F1s -F2 $F2s -Recycle $Recycles -Backup $Backups -BackupPath $BackupPaths
    }

    $watcher = New-Object System.IO.FileSystemWatcher
    $watcher.Path = $F1s
    $watcher.IncludeSubdirectories = $true
    $watcher.NotifyFilter = [System.IO.NotifyFilters]'FileName, DirectoryName, LastWrite, Size'

    $action = {
        param($sourceEventArgs)
        if (($Recycles -eq $true) -or ($Backups -eq $true)) {
            Check-Folders -F1 $F1s -F2 $F2s -Recycle $Recycles -Backup $Backups -BackupPath $BackupPaths
        }
        robocopy $F1s $F2s /MIR /COPYALL /Z /R:5 /W:10
    }

    $onChanged = Register-ObjectEvent -InputObject $watcher -EventName Changed -Action $action
    $onCreated = Register-ObjectEvent -InputObject $watcher -EventName Created -Action $action
    $onDeleted = Register-ObjectEvent -InputObject $watcher -EventName Deleted -Action $action
    $onRenamed = Register-ObjectEvent -InputObject $watcher -EventName Renamed -Action $action

    $watcher.EnableRaisingEvents = $true
    while ($true) {
        Start-Sleep -Seconds $Time
    }
}

$watcher = $null
$onChanged = $null
$onCreated = $null
$onDeleted = $null
$onRenamed = $null
...
$run.Add_Click({
    StartWatching -F1s $folder1.Text -F2s $folder2.Text -Recycles $Recycle.IsChecked -Backups $Backup.IsChecked -BackupPaths $BackupDir.Text -Time $rptime.Text
})

$window.ShowDialog() | Out-Null

if ($watcher -ne $null) {
    $watcher.EnableRaisingEvents = $false
    Unregister-Event -SubscriptionId $onChanged.Id
    Unregister-Event -SubscriptionId $onCreated.Id
    Unregister-Event -SubscriptionId $onDeleted.Id
    Unregister-Event -SubscriptionId $onRenamed.Id
    $watcher.Dispose()
}