When doing a workout, I have a lap power field that I use for targeting intervals - let's say I'm supposed to do 250w for 5:00 (not using ERG mode or anything like that). Initially after I hit the lap button the lap power will jump around due to a low number of samples but stabilizes fairly quickly. The weird part is let's say it's stabilized around 252w (or whatever), every 5-10 seconds it will show something like 241w for 1 second and then go back to the 252w. It's really annoying because if I happen to hit the lap button to end the interval just as it goes to that lower value, then that lower value is what gets recorded for the lap.
It's not dropouts. If I'm 4 minutes into an interval, it is mathematically impossible for an average to go from 252w down to 241w and then right back to 252w one second later. I'm also not seeing any zeros in the data.
Does anyone else see this? This is something I have observed with every Garmin I've owned (a 520, 530 and now a 540) and it also occurs on my wife's Garmin 530.