Did you finish the flight? If so, and you have closed the acars program, flights remain on the map and move to that location as it is not getting info from the acars program anymore. To change that, edit your local.config file and change the following settings
Config::Set('ACARS_LIVE_TIME', 10);
that is defaulted to 720, change it to a lower number like 10, means after the flight the flight disappears from the map and that problem is not encountered.