Powershell error when using FileSystemWatcher

Question

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()
}

• Luuk: "Please tell me what I did wrong and how I should fix it?" Please provide a minimal reproducible example (without ... in the code.)
• Luuk: Please try to debug you own script, using: How to Debug Scripts in Windows PowerShell ISE
• lit: Debug using Visual Studio Code. code.visualstudio.com/download It is the right price (USD 0.00). ISE is no longer under development.