I was having trouble completing Patrol missions on Venus involving collecting materials from enemies. I completed one in The Embers without issues, then it took a half hour to get one drop for the next mission I took (same area). I abandoned the mission, then moved to The Citadel. I took another gathering mission, and did not get a single drop through another 15 minutes of play, including through a public event (and yes, I was killing the correct enemies for the drops). I also noticed that there were no ammo drops from any enemy during this time. I understand that it's mathematically possible for this to happen since drops are random, but going that long without a mission item dropping or ammo dropping doesn't make sense.