7.60 on Fenix 5X Plus, walking/hiking heart-rate off

Ummm ... I blindly assumed that they were separate, because until 7.60 I never had cadence data on rides even though I often do a ride into work one day, walk home and then walk the next day and ride home. 

Garmin don't understand running power meters. They just understand power meters (and they assume that they are only for cycling, so the power fields are only available in the cycling activity app). So your Stryd is connected as a power meter, and of course Garmin will use if for cycling unless you have told it not to.

So unless you can point to a place in the settings where you could configure the watch so it would not use your power meter in cycling, I find it hard to believe that you had your Stryd connected as a power meter, and the watch did not use it for cycling activities.

What I do find easy to believe is a whole other explanation:
You didn't have your Stryd connected as a power meter until recently. Instead you used Stryd's own Stryd Power data field to show power. This field will show and record power, even though you don't have your Stryd connected as a power meter, because it creates its own ANT+ connection to the Stryd. Then recently, you decided to also connect your Stryd as a power meter, and suddenly power data started showing up in your bike rides.

The cadence part of your experience I can't explain, though.

Am having the exact same issues. Just back from a week holiday which included 3 days trekking and 3 days open water swimming training. 

On the trek, GPS connected and logged (somewhat accurately) my distance but suggested that my heart rate during 8+ hours hiking a day rarely went above 80. Now I'd like to think this was because I am ultra fit but reality suggests this is far from the case. I was in 35 degree temperatures, climbing over 1000ft a day in 95% humidity carrying a 10kg pack. Manual checks on heart rate showed I was waaaaay above Garmin's read. My friends cheap Fitbit tracked everything perfectly...

Then to add insult to injury, I went off on the 3 day open water swim camp. Despite easily picking up GPS, Garmin completely failed to track my distance and would often stop around the 300m range. Very very annoying as ended up not having any usable data from the trip. 

I had multiple issues with battery drain on my Fenix 5s+ and had to contact the executive and board to get a replacement which up until recently has been fine. Then this issue started. I am trying to contact Garmin today now that I am back and am hoping my experience with customer service will be better than last time!

I am experiencing the same issue in hike , climb. Not always though. Eg last weekend, climbed Mt Shasta, first 5 mile leg fine. Second leg HR average of 88 above 120 for only 30 min. More likely above 150 for several hours.

@missfinch  ... I managed to source and install the old 6.64 beta, and with that the watch works as expected during activities ... however - a syn now takes over 10 hours (which is unacceptable) and bumps me up to the buggy 7.60 again even though "auto update" is turned off - even LESS acceptable.

I'm not quite sure how to deal with this, I have the strong suspicion that replacing the watch won't fix the buggy software. :(  

Have you reported your issued to support?  I can't believe that it's this few people who have this issue (or maybe not enough people to walking/hiking on a regular enough basis as an activity they record).

tinkster said:

I can't believe that it's this few people who have this issue

We all have the issue. Most of us just don't trust OHR for anything else than resting and light activity, so we use a chest strap for everything else.

Here is an example of 10 sets of pull-ups and chin-ups with a chest strap. The HR rise during each set is clearly defined. It is even visible that I did more repetitions in set 5 and 10.

Here is a recording with OHR for the same exercise. I am not even able to count the sets when looking at that curve:

(I don't really care about HR in that exercise. That is why I have recordings without chest strap. For anything where I need to know my HR, I will also use a chest strap.)

I hate chest-straps, and no matter what I try, on longer runs they always give me chafing. :/ ... that's the whole reason I gave up on my Suunto (well, that, and their app being crap).