Talked with my local HFO, they seem to think it is the low volt power supply, dropping out the relay that holds the coil of the contactor.
My K1 contactor had a noticeable buzz to it, compared it to the one in my SL20 lathe, that has no vibration.
Looking at the machine, seems like there is a small microswitch next to K1 that holds it closed, not sure about the "low volt power supply, relay", unless it was triggering the auto power off.
I have also been having a spindle drive fault, and z axis fault, where if the machine has been sitting idle, and it just faults out, and the head drops a couple of inches, that can be scary if you are setting the machine up when it does it. Hasn't faulted like this in operation though.
Anyhow I cable tied the micro switch shut next to K1, probably not a great idea, now I have no power off, but I did try it, pushed power off and it did the spindle fault alarm z axis...
... and it still dropped out, but I was able to observe the PHASE DETECT FAIL light go on a few times.