To add to the other suggestions, here's a list of the ways I've had failures to track a shot:
1) Low muzzle blast rounds that fail to trigger the unit. Examples are 22 rimfire and 32-20 out of a rifle. You can add an external trigger microphone, or position the muzzle closer and alongside or slightly behind the Labradar. Usually does not generate an error message.
2) Shooting with another person nearby who has a "big boomer" that triggers the Labradar. Then the Labradar starts looking for a projectile, but doesn't detect one. Usually generates an error message on the screen. The external microphone is very susceptible to this. Can adjust the sensitivity to reject nearby shooters.
3) The unit not aimed properly at the target. I've been lax at times in aiming the unit at the target and still had it successfully track projectiles, but I've heard of others who have had problems. If the Labradar triggers from the muzzle blast, I'd expect an error message.
I'm not sure if the offset value setting can cause errors, if for example 6 inches is set but the spacing is 12 inches or greater, or vice versa.
Early testing by Bryan Litz - writer of several books on ballistics - had failures to track .223 bullets with a concave base. I think this has been fixed, but I'm not sure.
Is the Labradar not triggering with no error message, or is it generating a failure to track error message?