I use an off-line geocaching app, Locus Map. I use it for recording my hikes.
I find that sometimes it records the whole hike and sometimes appears to switch off for a few minutes up to refusing to record most of the hike.
This is not because of inability to access the satelites used by the GPS because its easy to see if satelites are in sight. I wondered if this is a problem with the app or with something within the phones GPS.
Is the app shutting down mid hike? You can set the app to have unrestricted use in its settings. If it's optimised or restricted, it may be turning off before your hike finished
