Thank you for your reports, Tenno. We're fairly confident that we've identified the problem: You're all too good at Rescue missions!
If you're familiar with Rescue missions, you'll notice that you get a slightly nicer reward if you break the subject out of prison without setting off the alarms, and/or if you kill all the prison guards. The issue we've identified is that the Requiem Relic you're expecting was only given if you were in the lowest reward pool from the mission. A fix will be coming at the next opportunity. Until this is fixed, you can work around the issue and ensure you get a relic from the mission by allowing enemies to set off the alarms before you rescue the prisoner and don't kill all the guards before extracting.
Edited by [DE]Momaw