The Menagerie boss this week seems to have a bug where the plates that you have to capture do not spawn up. This has happened to me three times today on PC and I keep getting put into instances where groups are at the boss but the plates are bugged. I attached a video if that will help with the troubleshooting process. This prevents us from advancing the fight and getting our piece of loot.
I have also seen this on PS4 several times