I met Matt, but he did not tell me about it, so I am responding, now after my come back home.
Exactly this happened to Samantha in France and Orestes in Poland. In case of Sam, it was faulty XT60 connector, its male pins were soft (probably overheated during flights before, as the spring material is also contact material and that is bad design choice). Sections of male pin were compressed (missing gap) and connector was very easy to connect and disconnect. Problem was solved by quick replacing.
Orestes had Deans connectors, they are good with nice large flat contact area and separete spring material. So far so good, but this time we flew on dusty place and one piece of sand can convert flat contanct to sigle line contact or even single point contact and vibration during flight can cause this problem.
I recommand power connectors with multisegment contacts wit separate spring. And of course, keep it clean, periodically check and time to time replace all connetros, including signal and do not forget also SWITCH and its leads which are soldered (can break inside insulation) - that needs periodical inspection.
To the security. I know about problem of restarting, but it is hard to solve. The best way is to keep good health of installation, but it is not only that what can cause it. For example if ESC overheates, motor will stop and when it cools down it will start again. The only solution is to have sensor of RPM, real time clock and flash or eeprom, (or mechanical memory like spring powered "memory" activated in such case, or something based on battery voltage) to see if something like that happened. Yes, I am speaking about price of the system.
May be I can invent some "additional" device so in case that we have something reliable, we can "add" it to existing systems. So far I have wifi cut off operable by android which can be hooked between my timer and ESC, it can replace this feature .
............. BUT ....................
It cannot be 100% safe, it is absolutely necessary act with electric models as they can any time start, if the battery is connected or not, human can do any type of mistake (for example that is why I have always model flipped on back, always pointed to safe direction etc. when I am not at it, also without connected battery)