New mord skin bug

I've tested this with the base skin and some of his other skins but there seems to be a bug with Lord Mordekaiser to where enemies can walk out of the circle of Realm Of Death (ultimate of Mordekaiser) in some scenarios and sit there until the ultimate has ended. They become untargetable to auto attacks but can still be damaged from either your passive or abilities. Don't know if its just me getting this or if this is an actual bug that should be looked at cause if not then it will make the skin pretty much unusable do to the fact people can ignore your ultimate if they just keep walking.