It just had my unit upgraded from 3.818 to 3.819 to help fix this issue.
I was in Indy today and I get a few Ka band blips, then about ten seconds later it starts to ramp-up gets half way then shows 2 bogey's for a few seconds and I get the J out. When I stopped at the RL I looked over and saw the driver a had a Cobra.
When the light changed it happened again got a fairly strong Ka band alert showed two signals for few seconds arrows pointing behind this time because the Cobra was behind me, then the J out.
I don't get as many J outs with the 3.819, but when I do get them now they seem to be stronger and even more misleading than before. And not sure why the bogey counter shows two sources.