I can confirm this also happens to me on Xanadu, 50ql stone altar of Vynora smack bang in the middle of my deed (its about 40x40 the deed), no other altars remotely nearby (there's another vyn altar down at the coast but that's not even in local range, and they reported to have the same problem). And sometimes Vynora just takes a hike only to come back after x amount of time. It smells like a bug, I've never seen this happen before in any place I lived on other servers where there were other people with other altars nearby. If however not a bug, clarification as to why this happens and how to prevent it is much appreciated.