Environment: Citizen's Library defence point
I cleared this point of mobs when I went to hand in a quest, and by the time I had gone in, handed in the quest, dumped junk off in the vendor, I came out and the defence point was taken over by a foothold and at least 10 invasion mobs. Fortunately, I was able to climb up the wall and avoid them, but I wasn't really sure that many were meant to take over that quickly. It seems a little extreme. By the time I had climbed over, less than a minute later, most of the mobs had despawned, leaving only the foothold and three groups. Might be an issue with the spawning of invasion groups there since there was only one guy doing the thing.

Environment: Floating artifacts
There are two floating artifacts underneath the bridge hanging in midair. One is at roughly 6972,8445 and the second one is directly along from that. There is no way to get at them. I expect they were meant to be on top of the bridge, or on the edge of it and have.. umm.. slipped.