A few times I have been doing sprint work ( p1 pedals and 520 ) looking down I always see the 3second power in and around 1000 watts.
Then I go on Garmin connect to check ride and it only registers a couple of the sprints, can see heart rate elevations but only couple of wattage spikes.
Have friends with exact same problem with power coming from Garmin pedals. So can't be an issue with powertap.
Thanks Lav