Dumb Rift Spawning Question Sorry

In my new save, that has the same seed and settings as my old one, there are always so many rifts where I built my base. Usually at least 3 within maybe 30-40 blocks of eachother. I mentioned in another post about using the command to kill drifters last night. It just gets so so bad. They spawn in my very well-lit house (also mentioned in other post that my house is filled with lighting implements because of this).

We have two players total, and tried using the command to make sure there's no scaling per player. That doesn't seem to help at all. Just now, there are five within sight.

I've seen posts on here and the VS forums about accidentally building a base in "an unstable part of the world," but I have no idea what that means. Does that just mean a lot of caves around or something?

I'm sure this is somewhere easily accessible, and that I've just missed it. My game is un-modded - completely vanilla - just to save you a few words. ^^; Oh and I'm just starting year 2. This has happened since the grace period thing ended. No ramp up or nothin.