I just started playing this game 10 days ago so I don't know if there is a fix for this because when I Googled I just got people talking about having issues with the Cayde-6 quest. I've been stuck on the lucent hive quest part of Timeline Reflection since Day 1 of playing. I've repeated the quest about 50 times in the last 10 days. I even did the Witch Queen story to see if that fixed it. It didn't. I tried to just skip to the next story in the Timeline to see if that would progress the quest. But the quest is still stuck in my inventory and I don't have the exotic weapon that comes with completing the entire quest despite having the legendary weapon you get for completing step 4. I'm pretty annoyed with it.