Your manager will write made up notes with made up dates, they won’t interview anyone that doesn’t help their case against you. This is their chance to make up a fake case against you to see if it can fake a judge into ruling against you, and prevent you from wanting to sue. Opening the open door investigation will cause them to put a silence order on anyone that has real facts so nobody speaks the truth. Their manipulation and threat tactics will scare everyone you work with to turn against you. They will promise those that could help prove your case a promotion, bonuses, raises and even your job, telling them that their own job was being eliminated, so they feel their only choice is to modify their words to help the manager and hurt you. Then they will never give them the things they promised. You will lose your job, they will hate theirs, the manager and director will enjoy this game with no repricussions on them.