One thing you didn’t mention after trying back at home if you changed the battery again.
It’s possible the battery you replaced after your first flight is suspect.
Loss of GPS has already been discussed.
The .lrf files are the low res version of the high res (4K for example) files, allowing fast file transfer to you mobile device from your drone etc. Renaming the file extension to .mp4, as you mention, will allow playback of these files on...
Are you sure?
If you have an RTH height set to 50-metres for example, that is 50-metres above takeoff point. If you were then flying 50-metres below takeoff point and hit RTH the drone will climb 100-metres before starting its return home.
I would hardly call line of sight - a very limiting range. It wasn’t so long ago that a coupkr hundred metres pretty good and acceptable range for drones
‘Right now, we need to think only about avoiding impacts with trees, wires, and (very rarely) low flying aircraft.’
And anything that the drone may fall on in the event of a battery or flight controller failure.