Windows Form "Jumps" when clicked

This question is regarding a Windows form built in PowerShell using System.Windows.Forms - I intend to convert it to C# at some point, just hasn't happened yet. C# contextual answers welcomed.

So in order to make this tool appear more like an "app" verses another WPF thing, the control boxes were removed, along with the title. In doing so, we lose the ability to move the form. So I decided to write a nice little number to handle that, which you all may agree or disagree with. Anyhow, it works great on my workstation, laptop, and a remote session to a few random terminal servers. However, when testing with a user, the app experiences a "jump" when clicked on where this bit of code might be picking up on the mouse click. The form's icon still shows in the toolbar, but it's obvious that the form has gone way off screen, and cannot be pulled back to center. I am not 100% sure if it's the code, but I have a feeling. I cannot reproduce this on my machines. Please don't tell me how to get the form back on the screen, that is just a workaround. I appreciate any ideas.

$GLOBAL:ButtonDown = 0
$GLOBAL:FX = 0
$GLOBAL:MX = 0
$GLOBAL:FY = 0
$GLOBAL:MY = 0
$Form.Add_MouseUp({handler_Form_MouseUp})
function handler_Form_MouseUp{$GLOBAL:ButtonDown = 0}

$Form.Add_MouseDown({handler_Form_MouseDown})
function handler_Form_MouseDown{
    $GLOBAL:FX = $Form.Location.X
    $GLOBAL:MX = [System.Windows.Forms.Cursor]::Position.X
    $GLOBAL:FY = $Form.Location.Y
    $GLOBAL:MY = [System.Windows.Forms.Cursor]::Position.Y
    $GLOBAL:ButtonDown = 1
}

$Form.Add_MouseMove({handler_Form_MouseMove})
function handler_Form_MouseMove{
    if($GLOBAL:ButtonDown){
        #write-host ("X:"+ ([System.Windows.Forms.Cursor]::Position.X) + " || Y:" + ([System.Windows.Forms.Cursor]::Position.Y))
        $newX = $GLOBAL:FX + ([System.Windows.Forms.Cursor]::Position.X - $GLOBAL:MX)
        $newY = $GLOBAL:FY + ([System.Windows.Forms.Cursor]::Position.Y - $GLOBAL:MY)
        $Form.SetDesktopLocation($newX, $newY)
        $GLOBAL:FX = $Form.Location.X
        $GLOBAL:MX = [System.Windows.Forms.Cursor]::Position.X
        $GLOBAL:FY = $Form.Location.Y
        $GLOBAL:MY = [System.Windows.Forms.Cursor]::Position.Y    
    }
}