Have a 2020 Zero SR/S with ~ 5000 miles, primarily freeway commuting. As fellow ebike riders know, one of the first things you notice switching over from an ICE machine, is the near absence of vibration. The bikes are just incredibly smooth. However, in the last few months, I've noticed intermittent high frequency, low amplitude vibration in the pegs/grips that's proportional to speed (generally only higher speeds, but again, intermittent). I've put the bike up on stands and can't feel anything obvious bearing-wise in the wheels. I've also ensured belt tension is on the low-side of spec, as there are plenty of reports of early bearing failure in the motors. Coincidentally, the "Commissioning and Timing" maintenance item hasn't been performed, as my local dealership has erroneously omitted it from past service. I'm wondering if any phase slippage could be introducing harmonics that I'm perceiving as vibration. Would appreciate thoughts anyone has on this or other suggestions. Thanks.