The ESC will shutdown with MID or HIGH timing if the temperature goes too hot.
Try to free up the golden heatsink from the shrink as much as possible (earlier version) if the newer version, then you may need to remove the heatsink from over the shrink and then partially remove the shrink and then put the heatsink directly in contact with the metal. Also make sure your gear fan is above the ESC heatsink.
Shutdown may also be a glitch. Tear up an old PC and look for the colorful donut shaped circuits and then remove them form the pc board and remove all the wire and shrink and unsulation and you have yourself and anti glitch device.
MID timing is absolutely the best unless you want to sacrifice your flight time for a little more power (It is just noisier, not that much power from HIGH timing).
Roger's Law: If it is worth doing it, it is worth exceeding it.