[Joseph Smith]

From what I understand about the breakers, you can briefly exceed the 40A limit without tripping them. This has to be the case, because otherwise every time a team got in a pushing match where their CIMs experienced near-stall currents they would be tripping breakers instantly.

Edit: some quick research has illuminated the problem for me. The snap-action breakers are thermal breakers. This means that they trip when they reach a certain temperature, rather than the instant they hit a certain current. That's why you can stall your drivetrain for brief moments without tripping them. They also include an electromagnetic component that will trip instantly when subject to major surges, like what you would see from a short circuit.