Controversy isn't part of the equation here. You change from license A to license B to your project without asking permission of those that contributed under l

Controversy isn't part of the equation here. You change from license A to license B to your project without asking permission of those that contributed under license A. Some party uses the code under B and violates B, but not A. Their attorney argues that you didn't have permission to re-license from all contributors, so the switch wasn't possible. You try to contact all developers that committed under A. Sadly, one of them died a year ago. To add a problem, that person lived in a legislation where you cannot give away authorship. Suddenly, you are in a legal mess. You can choose to follow through or drop the case.