In the Lien case we were first told that she had left of her own free will, then it was changed to that tale about writers not capable of writing for the character and that was all a "mutual agreement". I can also recall two events when members of two very famous rock bands had left the bands due to "mutual agreements" and it was many years later revealed from all parts that the both members were fired, one because the other members in the band simply wanted another person to join the band and the other because he objected to the musical direction the manager and another leading member of the band wanted.
I must admit that every time I see the word "mutual agreement" show up when someone leaves a successful project under mysterious circumstances, then I get suspicious and in most cases I've been right in my suspicions.
This applies to everything in life. If you get fired from a job, dumped by a partner, bomb out at school make sure you come up with the perfect line to give people explaining it and make sure you stick to it. If you have only one line people find it harder to read between.