Yea the fob spawned for me as well a few times in the main base, while i had extra made a purge base next to it.
Its on the large ice lake near frost bridge on exiled lands so plenty of space for it to not spawn inside my main base lol.

At one purge they as well broke into the main base instead and stealth killed all my thralls n pets while i was dealing with some other npcs at my purge base.