It's a bug. Let's hope it's not a hardware bug, which would mean Apple had to do a product recall. Nobody wants that.
In the Audiobus forum they're reporting glitchy performance with USB audio interfaces as well. So this is probably a more fundamental bug related to the new hardware than just a little buffer bug.
I wish Apple had a big enough love to their customers/ community to send a representative to this thread and offer a statement like:
We're aware of the bug. It affects the new iPad Pro 2017 lineup. It will be resolved in iOS 11.0. Sorry for the inconvenience.
And then shut the thread. Then we would know, that they know, that we know... etc...
That would be the right thing to do, when serious bugs appear like this. And it would take a representative a minute to do it.
If they don't have it under control yet, they could say:
We're aware of the bug, and the team is working to resolve it in a coming software update. Sorry for the inconvenience.