I've never had it happen. I've only done a handful of 3+ hour rides on zwift though. I also use direct Ant+ connection via dongle to the PC. It sounds like there maybe some kind of timeout protocol programmed into the CABLE's firmware, but I'm just spit balling there.

I have a similar issue when I use my Garmin Fenix (which has a poor antenna design) to transmit my HR to my ANT dongle. If I sit upright, the watch rests more in the bend of my wrist, which blocks/covers the antenna's signal from reaching the ANT dongle. So I get dropouts early on and not later, since I spend more time in the uprights as I'm warming up.

What I'm getting at is that yours might be a mix of tech and behavior related. As you ride longer, maybe something sweat-soaked is blocking the signal from getting to the dongle. Or you're starting to sit in more of a way that blocks the signal. Or, you're putting a water bottle or wet towel in a spot that's blocking the signal.

Look at your graph and try to correlate the dropouts with hill climbing (sitting up) vs aero position and stuff like that. There should be a pattern.

---

----------------------------------------------------------
Zen and the Art of Triathlon. Strava Workout Log
Interviews with Chris McCormack, Helle Frederikson, Angela Naeth, and many more.
http://www.zentriathlon.com

the cyclic nature of that and the way you describe it happening after a long time leads me to think something is overheating. The HR monitor is self doesn't make sense so maybe the cable? Check it to see if it's super hot next time?

Is it limited to HR or are you getting cadence and power dropouts also?

---

---------------------------------------------------------------

https://connect.garmin.com/modern/profile/domingjm