Xbee 900hp freezes

i have two xbee 900hp one in api mode as coordinator, the other as router in transparent mode. the communication works well for around 12hrs , then suddenly the coordinator freezes and the solution has been to disconnect it from power and then connect it back again. why is the reason of this behavior?

Check your last few API frames just before the module stops responding. Most likely the issue will be a corrupt API frame.