I just finnish 2 times in a row the lost sector "Bay of drowning wish" in master without dying and in solo.
However, i didn't get the triumph related to the accomplishment of this lost sector with all the condition nor the one for just finishing it in master.
I would really like to know why but a least this bug is know marked on the forum.
Your game history shows master (attempt, DNF) -> master (attempt, DNF) -> legend (cleared, 1 death) -> master (attempt, DNF) -> legend (attempt, DNF) -> legend (cleared, flawless)
Can you redo it and get a clip of you opening the chest and showing the modifiers (it'll show the difficulty modifiers) without the triumph unlocking?