Read and Write to the clipboard

I have this snippet on Windows (VS2017 Community) on Unity 5.6:

public static void setClipboardStr(string str)
{
    try
    {
        if (Clipboard.ContainsText())
        {
            // ...doesn't matter if true or false - 
            // from here on, I can't copy+paste inside 
            // the game or outside until I close the app. 
            // If I had an error instead of try/catch or 
            // check if it contains text, the error will 
            // remain UNTIL I REBOOT (beyond the app closing).
        }
    }
    catch(Exception ex)
    {
        Debug.LogError(ex);
    }
}

Whenever I use Clipboard in any form, even when checking if it's text or not, it destroys the clipboard until I close the app. Now, is this a Unity bug? VS bug? Is there something I'm not understanding? What should I use, instead?