I've never had this issue before, but yesterday while getting a traffic service from Boscombe Zone, I was asked if I was flying in formation with another aircraft. I replied saying that I wasn't, and the controller said it was weird as another aircraft had been following indicating about 200ft separation. I've never encountered this before, the HEX is set to the aircraft. PilotAware is the only thing I could think of as to why it was showing two aircraft, but I'm not quite sure why. Any ideas?