Just to let you know, I'm experiencing a lot of sound bugs with the new world editor and wc3 reforged in itself currently, just like in your video. So it's certainly not a map-specific problem and should be fixed by blizzard sooner or later.
For units in the distance it would be interesting to know where your camera is located. I'm guessing you want all sounds to be registered equally?
Either way, only idea I'd have right now is to create a point where each indiviual sound of every unit is played. But that sounds like tons of work and can't be the right way. :/
Edit:
There might be a way to offset the camera object (which registers position-based sound), but not the camera view. But idk!