20.26: No altitude change during activity (recorded wrongly as flat with 0m elevation)

1. No, I think maybe 1/10 of my activities or something like this. Haven't found a pattern really, might be several in a row, might be more than a week with no issue. As another user mentioned the temperature data seems to fail at the same time as elevation.

2. I can't tell if it affects this, as that data is so stochastic. It is not flatlining totally, as I have data.

3. Yes

4. Yes, but I'm terrible at reading my mail, so response may be slow.

Just upgraded to 20.31 and the same thing's happened to me. Elevation was flat until about 22 minutes into a run, when it suddenly jumped to the correct elevation. After that it behaved normally. Never experienced this before the upgrade.

Garmin-Sierra

1. No, this is an intermittent issue, and in my case the elevation was flat for just the first 22 minutes of the activity. At that time it suddenly jumped by 600' to the correct elevation, and after that it was normal.
2. Elevation is normal when not recording.
3. Yes, here's an example: https://connect.garmin.com/modern/activity/17287074595
4. Yes, you can contact me by email.

It happened again, no altitude on firmware 20.32 

I have the same problem. Firmware 20.29.

Possible workaround - I haven't seen this elevation flatline effect any time I do this, dozens of runs: after I start the run or workout, I switch to the elevation data screen and leave it showing until I see some elevation change recorded. So far, every time I've done this, I've not had the elevation flatline effect. Once I confirm active elevation numbers, I can switch to whatever screen I want and it stays fine.

Simply having the elevation data screen added to the run data screen set did not help. So long as I switch to that data screen after starting the activity, elevation changes get recorded. They're sometimes wacky, like showing 2X gain vs drop for a true out-and-back activity, but I can live with that.

-Only with bike activity both just riding or following a session or paired to an edge. Other activity is ok

-yes

-yes

-yes

Thank you

Same for me on a 255 !

I don’t think the elevation data page workaround actually works (not the version where you simply need to have it in the activity, and not the version where you need to look at it first.) Imo none of the cases where ppl have not seen the bug (when the workaround is employed) can possibly prove that such a workaround is effective (if you don’t see the bug you can’t prove it’s bc of the elevation page). But one case where it doesn’t work is enough to invalidate it.

I just ran a marathon with a big hill (with both climb and descent) at the start and a slightly hilly elevation profile the rest of the way. I happened to look at my elevation data page after climbing the hill, and most of the climb was shown as expected, but the chart showed a flat line the rest of the way. 

When I looked at the activity afterwards, the entire recorded elevation profile was completely flat (which is kind of interesting bc it suggests that the bug can either be retroactive or that the elevation chart data page can be misleading). It does seem that Garmin’s GAP differed from Average Pace from lap to lap in ways you’d expect for a non-flat elevation profile (disregarding the fact that Garmin’s GAP doesn’t work very well) so it seems that at some level, the watch knew I was climbing and descending hills.