Instinct 2X Altimeter issue

Not seeing that, its pretty solid esp over night.  Any chance your building is moving while you are sleeping or sleeping on a plane?

Mine is all right and stable when I am home:

Perhaps some dirt or moisture in the sensor port? Strong temperature changes? Forced ventilation, air-condition, or heating in the house?

Oh good call, perhaps a breeze / air flow near the watch?

Gonzo said:

perhaps a breeze / air flow near the watch?

Not really necessarily near the watch, but the turning on and off of the ventilation, cooling, or heating can cause slight air pressure changes if the windows are closed. And sudden temperature changes (such as putting the watch on and off the wrist, washing the hands, etc.) can cause changes in the sensor too. However, some dirt or moisture in the sensor port would be the first thing to look for. I recommend to use a good magnifying glass and a torch for inspecting it closely. Or a camera in macro mode.

Got this issue for weeks now.

When I am moving it seems to be accurate (hopefully), but as soon I stand still the Altimeter moves. For example, it does not matter if I am in or outside, I calibrate the watch and then without a single meter of movement the Altimeter stars going up or down. To me it looks like that the automatic switching between modes does not work anymore. I cleaned the port like Garmin suggested. 

it happens everywhere, even when I am sitting and my desk or at the kitchen Table, there is no air conditioning or ventilation. And also no rapid changes in temperature. I know that the sensor is very sensitive to stuff like that. But as I said when the watch was new I don't have those problems.

To me it looks like that the automatic switching between modes does not work anymore.

If there are so rapid pressure changes as shown on your photo, then they cannot be attributed to the barometric change (those are very slow and smooth), hence it is not surprising that the watch switches from the baro to the altimeter mode. The problem is not the watch, or the auto-mode, but the source of the pressure changes.

it happens everywhere, even when I am sitting and my desk or at the kitchen Table, there is no air conditioning or ventilation

As long as there is air-condition, heating, or ventilation in the house, it would influence the air pressure everywhere in the house, you do not have to be close to it. You can limit the pressure changes by keeping the windows open - that will either confirm or exclude the ventilation as the source of the pressure changes.

If not, I repeat my recommendation to inspect the sensor port hole very closely, using a magnifying glass, microscope, or a macro camera. There may be deposit of dirt, salt, or limescale that you did not manage to clean.

First, thank you for your answer. I am just wondering why the issue was not present when the watch was new. Did i get the auto mode wrong. I thought that the mode will turn off Altimeter when I don't move so changes in pressure will not affect the Altimeter?

Any Tipps vor cleaning the sensor port?

Looks fine with bare eye and a flash light, but it very difficult to tell

Did i get the auto mode wrong.

No, the auto-mode works as designed - fast changes of pressure trigger the switching from the baro to the altimeter mode. That's exactly how it is supposed to work. What you have to find, is why there are those pressure changes at all.

First of all try finding out whether the air pressure inside your house is really stable. Opening the window on a day with little wind should assure the air pressure is not much impacted by any air-conditioning. Using an accurate barometer would be another option to detect any pressure changes in the room.

Letting the watch on the table for an hour or two would be another test, excluding that the pressure changes are caused by yourself pressing against the sensor opening, or by your body temperature, sweat, mechanical motion, etc. When stable on the desk without moving, the impact of dirt or deposit should be minimized too.

Any Tipps vor cleaning the sensor port?

Garmin recommends dropping the watch for a few minutes into lukewarm water. I would tell rather for an hour or more. And inspecting it with the help of a magnifying glass or a camera in a macro mode, as I already wrote. Looking with plain eye is not really reliable enough.

If nothing helps, I recommend contacting the Product Support.

And I thought I was crazy - yes, I observe the same, probably since moved to 13.21 few weeks ago. During night altitude changes a lot (and I can attribute it with pressure changes as we have some fronts moving on in recent days) - during day - when I move - it's more reliable. I thought watch links altitude changes with movement, but it seems no more?

9820003 said:

I thought watch links altitude changes with movement, but it seems no more?

The watch does not know where the detected pressure change comes from - it can be due to a atmospheric change, as well as due an altitude change, or because of their combination. The watch tries to recognize known patterns (weather- vs. motion- induced), but that's not always easily (or at all) possible.

That's why I recommended letting the watch motionless for a few hours on the desk in a room with at least partially opened window (to exclude other pressure changes than the slow atmospheric ones). It should be on a day with no wind gusts that could influence the test.

Once done make screenshots of the graphs with the 4hr history of the altimeter and the barometer. That can give you some better clues about what is going on.