It seems the Labyrinth biome in Caves (Near Ancient Guardian) is not generating correctly anymore.
I don't have screenshots, but basically the Spider Dropper webs are generated outside the labyrinth ground including with certain Clockwork monsters and broken relic prefabs. They all float in the air and are not accessible by the player. Some of the said prefabs are generated correctly as well, but mostly stuff is simply floating in the air.
This is the server Map Generation log part, it has some weird entries: http://pastebin.com/UuVLYW4V
I don't know when this bug arose but i remember the Caves Labyrinth was ok at some point and without those issues. Recently wanted to generate a new map and noticed those issues. I tried to generate multiple maps, the problem was there every time with similar log entries.
Generate a normal Caves map and go explore the Labyrinth biome near Ancient Guardian.