I was spawned into an already in progress Haunted Lost Sector where the other two players had already killed 1 Headless One. We went on to kill all 14 other Headless ones where I damaged all 14. We killed the boss and I received my Manifested pages. However, the sector did not count to the 35 sector challenge (still 1/35 when I’ve done 2) and it did not count to the Kill all Headless Ones challenge (this I can understand a little because I did not damage the first one as that seems to be the requirement). However, if joining a session in progress doesn’t count then why are we matched in progress sessions. Hopefully Bungie sees this in case it’s bugged. Thank you and I’m still enjoying Destiny 2!