FWIW-
It has been a while since I posted about a very aggravating firmware problem with my E50 DAC.
It was bad enough and frequent enough that I had seriously considered selling the stupid thing, or even trashing it.
Also, I have since discovered that when it "randomly" resets itself away from my desired settings, it is basically resetting itself to the factory defaults.
This has nothing to do with the logical problem that in a DAC mode it should always be "on", but I digress...
I have long had a suspicion that it might have something to do with the IR remote sensor or perhaps the overly sensitive touch sensor on the front panel.
As a test I made an opaque flap from some cardboard and black electrical tape.
After setting the unit to what I wanted it to be (DAC mode, optical input, single ended output) I lowered the flap to shield the sensor from ambient light sources.
Those include multiple room and desk lights, and two nearby computer monitors, all of which are LED-based, and at least one of which is dimmable (via PWM).
Sure enough, the self-resetting nonsense has COMPLETELY stopped..!
It has been more than three weeks now without even one instance of odd behavior.
Prior to that I never knew what mode it might power up in.
DAC roulette.
And I have actually witnessed it changing right in the middle of being used on several occasions.
Apparently, combinations of pulsing light sources confused the sensor (an odd combination of circumstance, I admit).
The firmware just goes "tilt" and resets itself to the factory defaults.
Your situation light-wise will certainly be completely different from mine.
However if you may be having problems like that, you might try taping over the remote control sensor on the front of the E50 enclosure.
Costs nearly nothing to do, is totally reversible, and it might resolve the problem.
If you are using it in preamp mode where you need the optical sensor and remote control to be active, you might try placing a short tube or shade in front of the sensor instead.
Something that would limit the angle of viewing sensitivity for the sensor and shade it from most light sources.
This too might solve any instability issues.
Again this is just FWIW, your experience may vary...
I do hope it helps someone else.