It was barely felt on a mystic level. If it registered at anything at Stark Industries, it likely would have been at the bottom end on any scientific readings.
The source is that the universe is still unstable and copied from another. It could be ten years, a hundred years, or a thousand years before it fully stabilizes. It's on its way toward stabilizing, but a universe is usually a very old place where things have developed and settled in. And this one....hasn't. Yet.
I could be gone tomorrow too. There's no guarantees of continued existence. Not even in a stable universe.