I had the auto power off problem as well. I had three devices and only one was having the issue. I tested the auto power off option as suggested and it worked, but I had already got an RMA and sent the device back for replacement.
I got the replacement device and it too has the auto power off problem. I looked at the serial numbers of all three of my devices, and it appears that the one having the issue has the most recent serial number. I would have to guess that this problem is associated with the newer manufactured devices.
I have no problems with the auto power option disabled and will continue to use the device as such.