At what power? Yes, this makes a difference.
First of all, 60W difference at 100W or 300W is way out of spec. Either way, unacceptable.
- 100W vs 160W is ~46% diff
- 300W vs 360W is ~18% diff
Is this a Stages Left only? This makes a difference as well. If left only, then it takes the power from the left and doubles it. If that leg is stronger or weaker by say 3%, then after doubling you have 6%. At 200W, that is +/-12W. At 300W, that becomes +/-18W.
@BigOlBar Which Wahoo Kickr are you using? First gen Kickrs were notorious for being off by a lot. Newer ones are not w/out their own problems. Wheel on trainers such as the Kickr Snap can be quite finicky about setup in order to get an accurate, much less repeatable power number across sessions for the same effort.
The new Stages Gen3 spec states +/-1.5%. We will use the Kickr Snap +/-3% since it is highest/worst among the current Kickr series (i.e., Kickr, Kickr Core, Kickr Snap). Worst case scenario, this gives you a swing of 4.5%. At 100W, that is 4.5W. At 300W, that is 13.5W.
In summary, there are a lot of things to consider here. Even so, 40-60W is way out of spec!