that's not something I've ever seen. I don't think it's been reported by anyone in the blade or v9 forums either. the OS can reboot itself when critical system daemons repeatedly die.
Also we found a problem with the lockscreen. Sometimes system is laging and lockscreen is not responding for 5-15 seconds (as to me) and because of that tablet is going to reboot.
I don't know what is the problem. Previously, I think it's because of overclocking, but today one of 4pda users posted the same message. We are trying to change locksreen to Holo Lockscreen. Maybe it will help us
I would suggest you try going back to all default settings (including no overclocking, no zram, no lowmemorykiller alterations) and see if it happens again.
if it still happens then right after the device crashes and reboots do
adb pull /proc/last_kmsg kmsg_reboot.txt
and attach that txt file here. it might tell us something about why it rebooted. or alternatively you could try to catch the crash/reboot live with logcat. good luck.