Roddenberry's attempt to dump Doohan after the second pilot
I'm not up to speed on this. What's this about, please?
Apparently, according to Justman and Solow, after WNMHGB, Gene decided they didn't need a chief engineer after all tried to have Doohan fired. Doohan went to his agent and got that worked out PDQ and they wound up using the character a great deal.
I'm surprised Doohan and Gene were such good friends after that, unless Gene spun some yarn about it being a Network decision or some such.