While the intense speculation that Toyota Motor Corp. may have covered up electronic defects appears to have ebbed, Japanese experts say the world's top automaker deserves a failing grade for its risk management, and the resulting damage to its reputation was worse than it should have been.

They noted that the furor over the unintended acceleration issue may have been affected by multiple factors — overreaction by the U.S. media, a shift in the business environment, and the American political mood at the time.

But among them all, the company's delay in zeroing in on the problem from the very beginning led to harsher criticism against a company renowned for high quality, they said.