Why would spokes break at the flange early?
I've broken a spoke on a well-built wheel simply from hitting a bump in the road a little too hard. And on a generic wheel, I've seen that when one spoke breaks, the spokes at 90° intervals from it start breaking, even after I replace the first broken spoke. My guess is that this reflects a pattern of underlying stresses. So neither of your spoke breaks surprise me that much.

Since this is a Rohloff hub, you shouldn't have super-high tension on just the drive side due to dishing, so we can rule out that frequent cause of spoke breakage.

It might be fatigue. Jobst Brandt regarded fatigue failures as a consequence of failing to stress-relieve the spokes when the wheel was built.