I don't recall seeing duplicate tracks, however, network aircraft are hanging around much longer than they should be. This seems to happen when they fly out of network coverage, which includes landing at an airfield.
I've just watched UPS214 fly across the UK from east to west and it stopped moving about 15 minutes ago, however, it's still showing frozen in space off the NW coast of Wales.
I get the same problem around Manchester (EGCC) airport with a whole group of aircraft at about 600 ft and 130 knts which just won't go away.
My settings for Timeout are 30 seconds and hide 30 seconds, although I did change hide to 1 second to see if the aircraft disappeared - they didn't.