Again, If I understood you correctly, the reports I receive are not due to a bug. You also say this aircraft never gives out positional data ? Thus do you have any idea how/why this aircraft may appear to give positional data that matches my spikes ?
The positional data matches your spikes because they are both derived from the same source, so no surprises there.
However the source is invalid. The ATP in question is not equipped with either 1090 Extended Squitter or ADS-B.
However it is ELS-equipped and will send 112-bit packets (Comm-B Capability, Flight ID, TCAS RA, etc) in response to a ground station interrogation. RadarBox appears to be misinterpreting some or all of these responses as 1090ES Airborne Position Squitters (which are also 112 bits).
This phenomenon appears to be confined to RadarBox - I have SBS logs featuring said ATP going back to 2006 with no indication of any ADS-B capability.
I hope that makes sense, feel free to ask if you need any more background. Likewise AirNav, if you plan on doing anything about this bug I'm happy to provide as much information as I can.