I have a Wahoo Kickr Snap – the one with the bike’s tyre running on a steel wheel. Software Zwift. Besides plenty other Zwift-related irritations, I sometimes find that my power output varies substantial from one day to another, yet heart rate and perceived effort is the same (and route is also the same). Watt readings can vary + and – 20% for no reason known to me. Yes, I check the tyre pressure, and try to keep the wheel to IDT slip resistance constant. Yes, I do a “spin down” every few rides …. What else should I do to achieve more constant power output?