[[SPOILERS] [PC] Update 23: The Sacrifice Quest Bug Report Megathread]

During the quest, after i finish the umbra blueprint i went to the equip it and it played the cut scene where he grabs you by the neck and throws you against the wall, etc.. after that cut scene you are suppose to go to a mission and fight the umbra. Not sure of how the fight was suppose to go i decided to change my frame and when i tried to do so i realised i already had the umbra equipped. Initially i thought it was part of the quest so i rolled with it but quickly realised that it wasn't meant to be this way and the quest kinda lost its magic fighting with umbra excal vs umbra excal. I'm not sure how it happen, i just went to the arsenal and he was there ( i think its because i change loadout slot before i equip umbra and trigger the quest cut scene, not sure tho).

I was next to my brother as we both did the quest he did not experience this. he was only able to play with umbra later in the quest which is what i think you are suppose to do. 
I don't really have evidence of this as i already finished the quest and forgot to screenshot or record.