Lots of discussion about when to calibrate but where the data resides hasn't come up. I presume it's in firmware something like EPROM and won't change.
All the sensor data is continuously updated as well as the satellite and GPS info and location. It's like a mini computer that keeps updating maintaining all the telementry information and altitude and sensor info and feeding it to the main board as well as you input from the Transmitter for its flying instructions. The onboard computer so to speak takes over incase of a loss of signal and then initiates RTH via GPS home location and knowing its location so it gets proper direction back to you al by its itty bitty self. There are hundreds if not thousands of instruction be computed in nano seconds to properly maintain its proper flight and control.
I suspect that this system gets an erroneous reboot and the information is lost or scrambled and hence it no longer knows where it is or where it's suspose to go and hence a fly a way... Just like on a computer and your on the third page of your document and it reboots.. It goes back to default but all data is lost you were working with. Doesn't happen to us all or often.. But can happen whether it be a power issue or a glitch. Nope can find or don't have any info to back up my suspicions just an ole timer who has been working on computers before we had internet or PC's. Just and educated learned guesstimate.
Though I don't understand why the phantom has to know which way to point via compass for low battery RTH. Seems the GPS should be able to drag it home.
Car GPSs don't seem to know which way they're going until moving. Then once moving they know which way is north or at least which direction they are moving and where they were and need to be.