I see dual-targets like this occasionally, and always assumed one was direct from the aircraft, and the other was re-broadcast from an ADSB tower. If that's the case, and if iFly can tell the two sources apart (not sure it can), then it's probably better to prefer the direct-from-the-aircraft transmission, since by the rebroadcast version will be "staler" due to the time to process/rebroadcast.
However, I suspect there may be something more subtle happening, because I often fly in congested airspace with dozens of targets, and while these doubled-targets are not exactly uncommon, they're also not exactly frequent, either. I probably see at least one doubled-target on a typical flight, but I don't see jillions of them.