The on/off problem has been a constant companion of Bryston's BDA-series converters. I have had problems with my own BDA-2, have read about other people problems with their BDA-1 and now I am reading about problems of the BDA-3 owners. While this is not a critical issue as BDA is generally excellent, both in terms of reliability and stable connection, it is an annoying issue nonetheless.
I have done many, many tests to try to discover when and under what circumstances do these hold-ups occur but came up with no definitive conclusion. What I did discover is that turning the machine off with USB as the selected input is when the machine will sometimes stop responding while it's in standby mode. The AES connection didn't cause any problems.
I am not an expert in this kind of technology but my instinct tells me it must have to do with power supply that power the machine while it is in standby. Many devices like these have dedicated power supplies for these applications to allow for lower power consumption while in standby mode and these are usually powered by pulse-type transformers as used in modern mobile phone chargers. They are, of course, more than adequate for the job since the very instant the machine is turned on, it is powered by it's main power supply which is one of Bryston's many good design features. I have had similar problems with DVD players in the past so this is where I'm coming from.
We will never know for certain most likely.
... and this post is not meant as a criticism of any kind but rather it is my wish to support Bryston's efforts in maintaining their clients as one of their resources.
Cheers!
Antun