I have a uAvionix Echo ADS-B in and out on my LSA. I was flying cross country with my instructor yesterday and then about 5 minutes after takeoff Foreflight chimes in with something like "warning traffic very close, 6 o'clock, 100 feet below." My instructor and I look at the screen and sure enough it has a traffic symbol with our same course and a -1 then a -2 but no tail number. So we make a radio call and gain some altitude and the traffic follows us. I'm thinking that I'm hoping it's not a high wing but we were the only plane taking off at that time and we decided to pull out of the pattern at a weird time so it's not a common course. It looks light at this point that it's going slightly off right so I do a 360 to the left turn and it follows us. It felt like my WW2 flight sim days, it's on now! Jk, I figured it was some kind of ADS-B error. About a minute after that it disappeared and didn't reappear until our flight back. Actually now that I'm typing it out, I wonder if it reappeared in the same area... any thoughts?