I joined a Nexus strike in progress and found myself at Sekrion; the two players I joined had taken off about 20% of its health. We continued the fight per normal, taking out the waves of Vex that spawned before focusing fire on Sekrion. When Sekrion was killed, one of the other fireteam members departed. I don't know if they left of their own accord of if they were booted because of an error (I suspect an error because I didn't see them pull out their ghost). Sekrion exploded, and the two of us left ran to the middle, expecting to pick up the glimmer consumable Sekrion drops. Instead, we found ourselves face-to-face with another Sekrion at full health. One wave of Vex spawned alongside Sekrion 2.0, but as the fight went on, we found that no more waves followed. It was just us and the big guy for the remainder of the strike.
I imagine this is a rare (and therefore low priority) case, but I hope you can look into this. Having to kill the same boss twice was not fun, especially without the little guys to kill for ammo.
I saw a video where a raid group killed atheon and one guy left or got booted but everyone jumped into the middle and started dancing (they thought they won) the atheon respawn ed and killed them all, no rewards.
It must have so.ething to do with someone leaving before the event officially is over it causes a respawn.
This happened to me and a friend last night on cerberus vae strike, just as valus shattered in to pieces i got disconnected wit some error code, i joined my buddy as quick as i could and sure enough there was another valus with full health again, weird stuff