Correction........ Sorry but The parts are NOT out there and if you Crash your Mini 5 you are pretty much out of luck. There are NO Mini 5 parts available in the U.S. that I can find. Those that are advertised are shipping from China.
Except that the obstacle sensors don't work well in the dark and your Drone could lose its orientation, and wont be able to judge its altitude easily...It has a much better chance of ending up in a Crash.
All this worry about RTH altitude control malfunction is easily avoided by just flying the drone yourself. Better to be the PIC than a spectator.
If you lose position awareness for the drone, it's dirt simple to follow the rubber band line on...