I have a Fenix 5X that always loses GPS signal when I'm hiking in the forest. I understand that steep cliffs can cause lost signal if the satellite is on the other side of the bluff but whenever I have hiked in Sequoia NP, Yosemite NP, and Mammoth Lakes, CA my watch will just stop tracking and tell me it lost GPS. when I look at my track after my hike it's obviously shorter and full of straight lines where it connected the dots between lost and connected status.
I was accepting this as "normal" except I started using my Phone and Strava to track the same hike and Strava never lost signal.
Also, my girlfriend used her Apple (I use an Android) and the apple fitness app to track and she also never lost signal.
lastly, I hiked Yosemite with my sister who has a Gamin Forerunner (?) and whiteout fail her watch tracked the hike perfectly.
so, is there a problem with my watch? it's over a year old so not sure if Garmin will cover it but I got it from REI who has a liberal return policy.
it works flawlessly when I'm in my home town (San Diego) doing local hikes and mountain bike rides, the issue is just when I'm away from town in the forest but I have two phones and another Garmin watch that all seem to outperform my watch.