RENURPP,
The false indications I have experienced are all over land, can't speak for the REX's inbound track from AD but suspect they were over land.
Zaon MRX PCAS, works on the basis of receiving a signal (1090 Mhz) from an interrogated transponder unit within 5nm and 5000' (can be zoomed down if required). The other parties transponder needs to be interrogated from either a ground based ATC radar within approximately 150nm or from another aircrafts TCAS, typically overflying jets, within 40nm.
The typical indication I am getting is various ranges from 0.5 nm to 5 nm and below and indicating at or about ground level. There is no traffic I am 100% on that. No azimuth info on this unit, only altitude difference between you and them, range and whether they're climbing or descending relative to you.
This all sounds just like what the REX flight seemed to experience with their TSO'd system.
No warships in visible range, two gypsum/grain ships docked at the wharf though.
M