Today was the first time ever that my P4P was in the middle of the mission and it just came home and landed for no apparent reason with the battery at about 62%. I let it land, I checked the battery indicator on the P4P and it was fine so I clicked on Resume and took off again. It resumed normally and flew until the battery change was needed (as normal). I did not press anything or touch the iPad screen at the time it came home. It just did.
Posting this up in case someone else experiences the same thing.
This was a small 1 acre job. Flying at 75' AGL. Using iPad Mini 4. Latest software on all devices.