Help diagnosing random shutdowns in JB after root.

[jmonty42]

So I just got a replacement (refurbished) Droid 4 from Verizon after I bricked mine (don't tell them that). It came yesterday with JB already on it. I tried rooting it and the Droid 4 utility by Matt went through the motions, even installed the Superuser app, but I didn't actually have root. So I flashed the JB system with the utility and then rooted it. Ok, everything seemed to be working fine. I install most of my apps from before and start Google Music downloading part of my music library and go to sleep with it plugged in. My phone stays on the whole night without a problem, the alarm goes off in the morning and wakes me up for work just fine. Google Music is still downloading because it keeps losing Wi-Fi signal (mostly due to my router that is going out - I THINK). I unplug it while I get showered and ready for work and when I come back it has shut off. So I turn it back on. I listen to music on it the whole way to work (not plugged in) without any problem, about 20 minutes.

Now for some reason as I'm sitting at work with it in my pocket it will suddenly do a quick vibrate (I have it silenced) like I got a notification. If I check it, nothing shows up - there are no notifications or anything. If I wait a bit longer it will do another short vibration followed by two or more vibrations after a short pause - almost like I got 3 or 4 texts messages right after each other. When I hit the power button to unlock the screen, nothing happens. It seems like it's off, but I have to hold down the power button for a long time before it finally starts up again. It only does this when it is not plugged in. If I have plugged in, it just sits there happily and doesn't have any problems - no phantom vibrations either. It has also completely rebooted on its own without my intervention, too.

I thought it might be the wireless, so I turned it off and it still did it. I thought it might be something I had frozen with Bloat Freeze, but I unfroze everything and it still did it. My data signal is weak and one weird thing is that there is no 3G or 4G icon in the notification bar sometimes. I can see where it's supposed to be: there's the clock in the upper right corner, then a blank spot, then the icon for my alarm then the icon for vibrate. Sometimes it's there (I've seen both icons), sometimes it's not.

I didn't have this issue at all on my last Droid 4 in JB. I had it rooted for about a week before I bricked it. Have I gotten a defective unit from Verizon? Is there a good way to tell what is causing it to reboot? Any diagnostic apps or anything like that? Why is it vibrating when there doesn't seem to be any notifications at all?

EDIT: Also it never vibrates without reason if the screen is still on. I used Battery Manager to set the timeout to never and it never vibrated or shut down. It only vibrates randomly and shuts down if the screen is off.

EDIT #2: Alright, this last time that it went black I had a notification from a new email (from before it became unresponsive). The green light from the notification was still blinking even though the screen wouldn't come on from pushing the power button. It's like once it gets into this state for some reason the power button stops working (except to reset it).

EDIT #3: I've started going through my apps one by one and uninstalling them to see if the problem still exists after each one is gone. I've gone through a handful of them already. I think I'm going to have to factory reset this piece of crap tonight and install everything one by one to see where this problem comes up. I actually suspect it may be the Superuser app that was installed. It's a different version than what I've used before. Can that be uninstalled and replaced like any other app?

EDIT #4: I've done another factory reset and that didn't change the behavior. I flashed the SBF from a different source using RSD Lite and it is still happening. I am pretty sure this is a defective phone. Thanks for all your help and suggestions!