In the Birmingham incident, I wonder if the CAA felt that there was more to it, and that the "I thought the radio had failed" wasn't a genuine excuse. In other words that the pilot intensionally ignored ATC and decided to blame it on a radio failure?
It would explain why they decided to prosecute, but it would be hard to understand why a pilot would do such a thing.
Maybe I'm grasping at straws, but can't help but feel that there is more to it than in the summary given.