Had me a Clear quest yesterday, either Tier 1 or 2, at one of those small outdoor campsites. After killing and looting everything, I noticed the quest hadn't been completed. My buddy and I looked all around the POI, wondering what we could have missed. Turns out, we didn't miss anything...not all the zombies that required killing had spawned yet. Around two minutes after killing what I had previously thought was the last zombie at the POI, more zombies started spawning in a tent we had already cleared and looted. Around five ferals suddenly came busting through the side of it, despite the front having a perfectly good dooryway to pass through. After killing those newly spawned zombies, the quest status changed to show it had been completed.
Not sure why it took so long for them to spawn, but during my buddy's quest we had done right before that (either Fetch or Hidden Cache) we cleared the building, and while looting and looking for the quest's Courier Satchel, zombies started spawning again...several minutes after we had already cleared those same areas of the house. In fact, I walked into a very small closet, to open a box up on a shelf, and two zombies spawned RIGHT BESIDE ME...one was a cop, in the back of the closet, and the other a businessman, who was in the doorway on the other side of me.
When I say RIGHT BESIDE ME, I mean exactly that...I was pinned in the closet between the two zombies, unable to move due to their spawning on the blocks on both sides of me, pinning me between them, as well as blocking the doorway and my escape. I cut loose with my AK on the businessman, killing him and clearing my path out of the closet. After killing him, and the cop from the other side of the room, I went to help my buddy finish off the other zombies in the house that had magically spawned well after the previously spawned zombies had been killed.
TFP, y'all really need to fix the late-spawning zombies, and we also shouldn't have them spawning on the blocks right beside us at that, especially not when it pins us between them in a three-block space.