The weak link in all exteranl drives and video servalance is the power supply it is best to replace with 12vdc 3amp 4 amp is best
ive collected serveal NAS boxes and servalance recorders all needed new power supply only "Keep voltage " correct and always increase amp at least by 1 amp out to 4 amp raided will last longer
Always eject external drive no exception or power off system

Go to tiger direct or new egg for the best prices. Make sure that the power ratings on the new one is the same or higher than the old one.