streaming load type works only occasionally

I’m using Unity 5.6 and trying to add some musical elements to my project. On two of them the “streaming” setting works great. In all the others, it fails, and I have no idea why. I’ve checked and double checked and I don’t see any different how these are set up.

Compressed in Memory doesn’t always work either. However if on any of these audio sources I stream the audio from a url, then it’s fine! But then I hear artifacts in the sound due to inconsistent streaming, that’s not good enough.

Any idea of what I could be doing wrong?

anyone? nobody i’ve asked seems to know much about unity audio settings, unfortunately.