Last week, I would continue to have the buff for prime engrams even after I got one. I would kill an enemy, an engram would drop, and I would pick it up, and then turn it in. After this, I would still have the Prime Engram buff, and a few hours of grinding later I would get another prime engram. I think I got 3 per day maximum, but the buff remained. Today, I got my first prime engram, and now suddenly the Prime Engram buff is gone!!! Can someone please explain this?