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

Some weapons, such as the Akstiletto Prime here for example, are not properly using the right thumbnail. Others, such as the Fragor and Fang Primes, don't fit their thumbnail at all. Also Excalibur Umbra does not appear in the inventory screen under Warframes.

Not to mention the bug most, and I have encountered, have mentioned where if you un-equip and then re-equip Umbra after receiving him for the first time before completion of the quest, it will softlock the ui and prevent you from continuing. The only way to fix it so far is to join a party with a friend, go into the arsenal and equip Umbra, then when the UI softlocks have them load a mission and force it to start so you're ferried in as Umbra. After the mission you remain Umbra and can again use the UI and continue the quest.
Also suggestion is to replace Loki's decoy with another Loki that fights back instead of just bullet sponges. Sort of like Umbra can do when in spoiler mode.