Mine just switched off in the middle of a call and refused to boot after holding the power button, battery was ~70%. I tried multiple combinations of power button and volume keys and it didn't switch on. I waited a couple of minutes and then tried again by holding the power button for approximately a minute and it finally switched on. No idea why this happened and not sure if it'll happen again
It was on the .174 version, I had also installed the .167 version when it was released. All updates were through FOTA.
Haven't faced any crashes or reboots but randomly switching off and refusing to switch on is worrying.