Performance

[Kunter]

Is the time of the day specific? Like "daytime is good but late afternoon not so much?"
You may have an electricity issue... before my Torus isolation transformer, daytime listening sucked considerably compared to late nights...

Or, you may try to reset your Devialet's (long press the front button, it will start countdown from 5 and reset). maybe something going on softwarewise..

One more suggestion...

If you are using AIR for playback through a router, try booting/resetting the router...