Low Heart Rate in Aero Position

Does anyone have experience with low heart rate that is occurring only in aero position? my is unnaturally going low (sub 100bpm) during sweet spot and endurance intervals. It occasionally rises to my normal tempo and endurance zones. I’ve been experiencing this with both my garmin chest strap and fenix 5s. I wonder if there is something about garmin’s standard calculation of HR that is causing a misreading.

When I am sitting upright on the bike, i seem to get more consistent results, but have seen a few low HR readings.

When I run, my zones are consistent and predictable.

I don’t put too much weight on HR for the bike, but it’s happening often enough that I’m wondering if I should go see a cardiologist. Everything else feels healthy and fine.

Let me know if you have any advice/suggestions. Thanks.

My heart rate goes down in aero position, by a few BPM for any effort. However, what you are describing has got to be something going on with the sensor.