Amen, that kind of thing drives me crazy. After Sunday outside ride I had it happen for the first time in a long time. Too busy at work to track it down, too OCD to let it go.
Dredging up an old thread. I finally got pissed about the occasional TP 5-sec power not agreeing with WKO/TrainerRoad/Garmin. So I filed a support ticket and this was the response from TrainingPeaks support rep:
"The 5-second power is a known issue, TrainingPeaks uses 6-seconds worth of data instead of 5 to calculate 5-second max power. This dates back to when that code was originally written when power meters first came out most of the files were coming from SRM and the first powertap hubs. Those units didn’t actually record data every second, it was closer to every .85 seconds, so if we chose to use 5 samples it would be less than 5 seconds, and if we chose to use 6 samples it would be a little over 5 seconds, we chose to use 6 samples since that would be inclusive of 5 complete seconds, and that’s just the way it’s always stayed. "