when I was in Cyclopes lane trying to get the blue ghost from Akillies I found Cyclopes on the sidewalk then it went through the rails.
It's a glitch, it happens. It's not a big deal because usually those mobs (it happens in Unicorn Way with fairies and other places as well) don't pull you into battle.
I have had the same issue! Except it was from a gobbler somewhere in Colossus Boulevard. At the time I was going to fetch the Obsidian chest from the final boss in Colossus Boulevard.
When I was going to battle a boss in Wintertusk when he was roaming around he went through the walls but once I joined the battle arena where the henchmen was he went back. I assume it is a connection or lag problem.
Well this does happen all the time healer it is true no one likes having it but still its fine it happens when your computer is probably not right or connection if your computer is old then you might not be able to fix this problem i had a old laptop now i have a 4000 dollar computer and i never have these issues so that may be the issue old computer im not saying that you have to buy a 4000 dollar computer but its what i did anyways hope it helped bye
but still its fine it happens when your computer is probably not right or connection if your computer is old then you might not be able to fix this problem i had a old laptop now i have a 4000 dollar computer and i never have these issues so that may be the issue old computer im not saying that you have to buy a 4000 dollar computer but its what i did 
anyways hope it helped bye