Solution for me. So I had fully completed the Saint-14 quest on my Titan, but main a Hunter. I fully completed the entire Saint-14 quest line on my Titan, but had actually ONLY completed the final portion of his quest with a friend on my Hunter. When I picked up the “Corridors of Time“ quest from Osiris, he also had the remaining Saint-14 steps quest I had not yet completed on my hunter, (which was basically all steps leading up to his final stand with the fallen, which was completed). I’m not certain if me having these quest steps incomplete on my Hunter was what was messing up the Bastion quest drop, or simply having it in my inventory on one character at the time, (my Titan wasn’t getting the Bastion quest either, but I didn’t do the Corridors quest on him), but completing those steps on my Hunter fixed the drop. Despite it being a bit dumb that Saint-14’s quest line is linked to Bation’s quest drop, that was clearly the issue for me. TL;DR: MAKE SURE OSIRIS DOESN'T HAVE ANY ABANDONED QUESTS OR THAT YOU DON’T HAVE HIS INCOMPLETE QUEST IN YOUR INVENTORY. Hope that helps someone out there!