I've been using vari for 2 years, minor problems with connection with Edge 830, but never a problem with car detection. My friend bought a new varia. We ride together in the peloton and my Varia only detects cars at the distance between me and my friend. When I ride at the front after changes in the peloton, he has the same situation.The one on the back of the Varia works fine. The one in front has a range of up to the nearest radar.
I have traveled many times with someone who used Vari and there has never been such a problem.
Any idea what to do? Both models are Varia 515