Hi. As far as I know, you do not complete Echoes if you die before using the portal out, after completing the mission in an echo. However, I just died at the same time as Orobyss, and was rewarded with timeline stability regardless (I would’ve assumed that I lost the timeline stability since I did not leave the area before dying).
Not sure what the intended mechanic is here, but wanted to inform in case it’s a bug.
Br,
Marante