Hi from Germany. Same here with my four days old MB Pro. I just had a call with the Apple support. My impression is that they know the issue very well, because I explained my problem and was immediately strongly recommended to go to the Apple Store and replace the macbook, because it supposed to be a hardware problem. However, after I have been reading all the posts here I am skeptical if this will help (I have more than a week left to decide whether to replace the mac or wait for Mojave).
My experience: When listening to music just on iTunes (on 48.000 Hz) everything is ok, for many hours. But when I start Logic Pro, the audio format switches to 44.100 automatically (and cannot be changed back to 48.000) and the problem starts after an hour or so. I could not find any possibility to change that in the Logic settings. Maybe the same with Garage Band, Blender oder any other apps? Seems like there is something, whatever, not adjusted correctly.
My experience: When listening to music just on iTunes (on 48.000 Hz) everything is ok, for many hours. But when I start Logic Pro, the audio format switches to 44.100 automatically (and cannot be changed back to 48.000) and the problem starts after an hour or so. I could not find any possibility to change that in the Logic settings. Maybe the same with Garage Band, Blender oder any other apps? Seems like there is something, whatever, not adjusted correctly.