I have four n-scale units from BLI all purchased in the past 2 months:
2 of the E-6A powered working okay on 5 August 2012.
1 of the E-7A powered returned to BLI for repair
1 of the E-6B powered returned to BLI for repair
I contacted BLI by telephone and was provided a return authorization number and instructed to ship the engines to them by UPS. I did so; engines reached BLI on 3 August 2012. I was told BLI currently has only one repair person, so repair may take 6 weeks, "due to back log I assume."
Some of the sound functions are muted when the 8 function key, F8, is pushed; primarily these are the engine motor sounds.
On my engines, some of the sound functions still play when the mute is on for engine motor sounds; these include F14 passenger announcements, F16 maintainence sounds, F17 radio sounds for example.
Some of the sounds functions such as the horn on the two units stopped working, so I returned the engines for repairs.
I have noticed that F14 passenger announcement function and F16 maintainence sound transmissions may activate when F14 is pushed. This happens randomly.
I am new in DCC and thus am not certain if control of sound functions could relate to the DCC control system.

I am using NCE for DCC and found the sequence for factory reset which takes the engine back to address number 3. This did NOT resolve the problems with the two units I returned for repairs.
Also the powered E-6B unit ran okay in reverse, but not in forward; initially sound function worked, but then some stopped.