Are you certain you know the "ghost" traffic is "ghost" traffic?
If the XRX has the same issues as the MRX, then in my experience, ghost traffic is pretty obvious with repeated alerts for something 0.5nm away.
As the previous poster stated, it is invariably because the host's transponder signal is a bit on the weak side and so confuses it with a threat. Never had a problem when flying the Cub but many problems in the Seneca. Turn the transponder off and see if they disappear.