Sensors Being Turned Off

Yes, I've noticed the same

yes, same behavior for me on F6 Sapphire. 

I did a 100km bike ride without knowing this because i forgot to turn them on(already knew i had the issue)

Now i'm checking that all expected sensors are connected before start. 

And also observed that sometimes the sensors remain ON, but then I find them OFF again on the next activity. 

Have you reported this to official Garmin Support? (unfortunately i did not managed to do it yet)

Unfortunately not yet. I plan to do it today now that I know it’s not just me seeing the issue. 

Perhaps it's defaulting to a power mode that has the sensors turned off every time you start the activity? I'm curious, do you use custom power modes? I found that all my activities were defaulting to "normal" power mode. I would change it while in the activity, but then it always went back to "normal" next time I started an activity, and perhaps "normal" doesn't enable sensors. From the main settings, go to activities and apps and check your specific activity and the default power mode. 

I found that all my activities were defaulting to "normal" power mode. I would change it while in the activity

What were you changing it to? "Normal" doesn't seem like an unreasonable default, going by the name, and AIUI that's just the settings you've set generally on the watch, it's the other modes that alter those selectively.

Either way I do not think this is what is happening here; I've seen the same, but some sensors turn off after an activity and others don't - for example my Tempe never turns off. Someone else has posted a thread about how their Tempe is always turning off with 11.10 but everything else is OK, so it's not particular sensor types.

I sent this in to the outdoor beta email address in the first beta where it turned up & the 11.10 release candidate, but didn't get a response.

(Edited for idiot typo)

That's what I initially thought too, that there was some power saving thing switching off all the sensors. I checked and all my activities are on "Normal" which I can't find any options for.

Like mcbadger said above, the weird thing is that my Tempe stays on all the time. It's just my footpod, speed, and cadence sensors that get shutoff after an activity.

I don't think it's related to any power setting. There are some posting identical issues on the 945 forum and the 945 doesn't have power modes.

forums.garmin.com/.../1131113

Took a look at that thread, good find on eliminating the power mode theory.

I've deleted and re-added sensors as suggested and still see them being turned off after an activity.

I factory reset mine hoping it would fix the sensor issue, along with the way the battery drain in watch mode has doubled, and it made no difference other than needing to start teaching it VO2max all over again & put all my settings back in. 

I saw this as well on both my F6 and FR945.  I tried everything with deleting/re-adding the sensors, but nothing worked.  I finally did a full reset on my FR945 and ever since haven't seen it on either device.  I didn't have the issue on my Edge.

Are any of you using multiple watches, or watch and Edge devices?

The one other consistency I saw was it would get turned off after I would look at the sleep widget in the morning and manually end my sleep.  Anybody else using the sleep widget?  When you first get up, try checking the sensor status, then "End" your sleep in the widget, and check the status again.