Problem:
UAD Apollo Twin USB Audio Interface is known to freeze occasionally by itself,
by which it not just freezes itself but outputs a terrible sound.
Solution for it simply to power off and power on again.
This does not affect usually any other software maybe except that you have to stop and start audio player again , just for example, even if you had lets say an audio playing in the background.
I do suspect that this freezes are somehow related to USB bus itself.
When computer is under heavy CPU load, then the UAD Audio Interface simply freezing with terrible tonal noises.
Maybe because while the CPU is overloaded then USB bus have delays in signaling or even loosing some data.
I believe that UAD shall fix that on the first place inside their own Drivers, however they never did.
Now about how it affects Unreal Engine:
Unreal engine 4, all versions starting with 4.12 and till the most recent 4.15.1 freezes totally (becomes not-responsive task) just in the moment when UAD freezes.
After restart of UAD the UE4 keeps to be frozen.
The only way to continue working is to use TASK manager to kill the UE4 process.
You can easy replicate this problem by running (ex.) Substance Painter in Map-Baking mode with Normal + AO etc.
The CPU load will be heavy enough to overload the UAD USB and cause the freezing.
Same can be caused by just running Build function on a larger project in UE4 editor.
In my personal experience the Substance Painter causes the overload much faster (from few seconds - up to a minute depending on project complexity)
Other info:
CPU: Intel i7-6950X (not overclocked)
GFX: Titan X Pascal (not overclocked)
Memory: 128 GB (Running in normal mode, but is capable to be overclocked at least twice of its current running speed)
Audio: UAD Apollo Twin Audio Interface USB3 version (with latest drivers)
OS: Windows 10