Let me start off the message by mentioning that I have been a (altogether) very happy user of cyanogen mods with my last 3 android phones.
The last and current (but it seems not for long) is an HTC One X, which is over 2 years old.
This poor thing has gone through so many ROMs that I have lost count.
It is currently running on a stable cm10.2.1, upgraded from cm10.1.3.
I have experienced sudden power offs when there were obvious battery drain, battery overheat, weird app installation issues, especially since moving to cm 10.2.1, which also caused the GPS to stop getting any satellite signals.
However, the phone has recently (a couple of weeks) leveled up into a bizarre mode:
It will power off all of a sudden, the battery levels are not low 65-75%, so I would assume it was just some process in the background, and go ahead and start the phone up again to go and check through the logs, or even disable/cleanup dodgy overreacting apps. But to my surprise, the phone passes the quietly brilliant screen, as well as the CM logo with the circling arrow and as soon as you can see the background it shows Powering off - the phone is shutting down.
For those brief couple of seconds I can see the battery indicator (top right corner) showing a small part of it in red, letting me believe the battery's status is critically low. So I let the phone charge for half an hour, and start it up again, with the same result, once the device goes past the logo and the background shows, the Powering off message appears again. The battery indicator is still showing a small red circulating section of the whole.
The next step was to go and check in recovery mode. The battery on the TWRP screen shows almost 70%, and this leads me to assume there is something wrong with the battery. But the phone is not turning off for as long as in recovery mode. I still haven't ruled out the battery issue, and will test it when I get delivered and replace the spare one I have ordered.
Reading through forums and other threads, there were people complaining that they had the same issues when the phone was trying to change from 2G to 3G and the other way around, so I removed the sim card and have restarted the phone, still the same result, powering off after boot.
I also reflashed 10.2.1 thinking that a clean installation will help getting rid of some new app/processes that might be causing this, but exactly the same powering off occurs after booting. The same happens even after a factory reset.
Usually, after half an hour of inactivity the phone would start up normally, but today it has been several hours and the behavior is not improving.
At this point I can't get into the phone other than on recovery, I can't copy from/into its storage anything, not even the nandroid backups I regularly do (and which stupidly I haven't copied over to an external storage). I could try reflashing some stock image, but even that I don't have on the internal storage.
So as you see, I am bit stuck. Phone will not stay ON long enough for me to connect to my machine and save my backups, or load any new stuff.
If you have any other suggestions other than this, or perhaps a workaround to what I have already tried, I would extremely appreciate it.