Upon some further investigation, it appears that what we have experienced is very similar to what is described here…
A Land UNDER the exiled lands
Last night we discovered that they were spawning underneath our most recently placed building blocks. Maybe that has something to do with it.
Oh, and if it weren’t archers every time, it wouldn’t be nearly as bad of an issue. We’ve lost more than a few pets because of this issue, and my friends are starting to get pretty upset about that.