Phantom aircraft triggering a TCAS RA
Good evening, a few days ago we were flying level in the hold, we saw an aircraft on TCAS that was +200 ft, following us for 1 complete lap, ATC was advised, they had nothing on their screen apart from us. VMC conditions, 8000 ft, we could not see anything. Then RA "Descend ! ", we comply, and then "Level Off !". There was no "clear of conflict" annunciation. We concluded it must have been a glitch from our TCAS system, did you ever experience this malfunction ? Both GPS were giving reliable information, both transponders as well, B 737 NG.