Hi I have an Instinct which I pair with a Garmin Cadence 2 sensor.
And I noticed that there are weird readings on the activity. Those strange triangular sections are captured. I assumed it was the garmin cadence sensor and swapped to 2 other brands of sensors. And they all create these weird "triangular" anomalies.
I run a Garmin Speed 2, Garmin HR and a Garmin Cadence 2 on my bicycle rides.