Missing a rep at the start on occasion? Some random submillimeter movement at the start that then transitions into a full rep can trigger the rep to be ignored. Normally, those micro-movements are followed by larger movements that are not reps (e.g. grabbing the bar then walking it out), which is totally fine. Overall, it seems like a very rare case unless you have the “magic touch”. One possibly related factor is where you have the Velos-ID positioned relative to the bar. Place the device under where you’ll lift, not under where the bar rests. When squatting, for example, place the device near your final foot position instead of back over at the rack.