Floors climb error

Hi!

I have an issue, related to floors climb counter, in the last weeks or so with my Fenix 5.

What is happening is quite strange, the counter is correct but it happens that it "cancel" some floors from the count. 

For example, this is happened more than once, I usually climb 5 floors to my office. The floors counter correctly increase of "5" (e.g. from 6 to 11), but after 1 or 2 minutes it goes back to the previous value (so from 11 to 6)! If I keep the watch connect to the phone, also in the app I see the same issues, it is updated to e.g. 11 and then revert to 6 after 1 or 2 minutes, so it seems something related to the watch.

It seems not related to the barometer sensors (by the way I clean up it), since the counter seems working. Is it something related to a software error? 

Can you help me?

Thanks in advance!

Regards