I've found a bug in Yggdrasil Tree and Comodo City.
There are some cells that should not exist.
Yggdrasil Tree>> Something like 12 cells, all of them in the right corner of the map, only reachable by Fly Wings and Teleport, monsters (Plants) also respawn in these cells.
Comodo City>> There is a cell in the middle of the sea, right in south of the map, a friend of mine get locked in there. Also reachable with Teleport and Fly Wings.
Although these are indeed bugs, both those maps are official, so the bug is from Gravity itself, fixing it means the maps have to be editted and then added to the heRO files and will make them larger.