Any chance the Edge was getting wet?  I've seen reports throughout the forum of funky readings if any moisture gets in the holes for the sensor.  Try warming for a while with a hair dryer, very gently (no excessive heat).

This looks like the same problem I have described in 

"Edge 130 Plus elevation accuracy is poor following switch off and on in mid ride".

Looking at your graph, the first descent is nice and smooth.  I'm guessing that you switched it off and on again.  At which point it only updates elevation every minute, and even then not accurately.  Hence your "stairy" plot.  Maybe try a few ascents and descents, then switch off, repeat and compare.

Yes, most probably this is the reason. Auto power-off is enabled, so when it is paused for a few minutes it switches off and I have to power it on before each descent.

Inspecting some other records with a similar problem (one from this weekend, I remember that it switched off a few times) I am quite sure that this is the reason. Did you maybe receive any useful feedback on why it is working as it is? Any workarounds (besides not switching it off)?
It is interesting to me that the position is accurate, only the elevation is way off.

I was looking for some Garmin direct contact email addresses but couldn't find any.

In the UK the email I have been using is [email protected].

I have just been on the phone to them.  I cited your case as another unit displaying this poor functionality.  They claim it is the first time that they have seen the problem, and have now raised a "Priority Service Case".  They're going to send me another unit, which I fully expect to have the same problem; however, they say that they will work on the fault in the meantime.

I got the impression that in the 3 working days between telephone conversations there had been no investigation.  So I will keep phoning.  UK number is 0808 2380000

Hopefully they fix this. I have been having the same problem with wrong elevation.

They have told me they are not going to fix it.  Very disappointing.   They have replaced my 130Plus with a 530, which appears to be a nice unit but unnecessarily complicated.  I liked the simplicity of the 130.

this is very sad. second thing that is braking my heart about garmin 130 plus. first is that it cannot have the battery pack extender attached.

I chose the 130 plus because of the simple display and overall simplicity. Somehow I assumed that battery life would be a non-issue via extenders or somthing and that it will just work. Ehh.

Will try to contact garmin support too about this issue. I do not want a touchscreen to be honest. Buttons are why I chose this unit.

I do have the same problem with inaccuracy after switching on from sleep mode. Once this happen, I usually lose informatin about regeneration (it says 0 hours) and training effect . This happens even if the device restart during the activity itself. Both issues persist since I have bought the device (2020).

So annoying

I do have the same problem with inaccuracy after switching on from sleep mode. Once this happen, I usually lose informatin about regeneration (it says 0 hours) and training effect . This happens even if the device restart during the activity itself. Both issues persist since I have bought the device (2020).

So annoying