Beaglebone black rebooting unnecessarily

Hi, i have ported android jelly bean on Beablebone black which is using chipsee 7’’ LCD touch as the GUI. I am using this board to get UART lines output and connecting it to external hardware and then i send/receive data to Beaglebone. The problem is after using the board for many days now the Android OS is rebooting by itself as soon as the UI lock screen comes up. This repeats even after flashing new OS on to the SDCard many a times. What could be the problem, please suggest.