Fenix 6 PRO Solar heart rate monitor make up data?

Hi, I am an happy owner of a Fenix 6 pro solar FW 25.10.

Last week I recorded a paragliding activity while keeping the watch in my pocket (i had too many gloves on to use it on the wirst).

I got all the expected data (temperature, GPS position ect) but i also got the heart rate plot with some strange values (39bpm means i died for a short time :) ).

I am used to strange data but somehow consistent (steeper hill->higher rate).

Have anybody experience something similar? How is the watch retrieving such data whithout being worn?

thank you,

paolo