Same problem for me: unable to advance the lament quest as the Exo Challenge will not complete even though I’ve run it 3 times. On Xbox using Hunter. In a fireteam of 2. My fireteam member has completed this step when we ran the challenge together. We completed the challenge as part of the Variks quest then again as part of the lament quest. Have tried being fireteam leader and with someone else as leader. No luck. Hoping this can be fixed soon...!