X-Plane uses 19 datarefs (plane1 to plane19) for multiplayer aircraft information.
And the IXEG 733 read these datarefs to show TCAS information.
The issue is how the VATSIM and IVAO client handle the datarefs.
Some examples:
1. When a aircraft is flying out of range or disconnects, the VATSIM/IVAO client do not resets the datarefs for that aircraft, but leave the datarefs with the last known values/postion. And the aircraft will show as a stuck target on the EHSI.
2. Sometimes (read often) the VATSIM/IVAO client can change the multiplayer datarefs for a aircraft, lets say from "plane4" to "plane6". The problem, again. is that the unused datarefs for "plane4" is not resetted by the VATSIM/IVAO client. So the "plane4" will appear as a stuck TCAS target on your EHSI.
Hope you understand my explanation
My script simply just resettes all the unused multiplayer datarefs.