Forgive me if there is some setting or obvious answer to this.

To clarify, I am ASSUMING that Rampant is the cause of this because it's the only mod I have installed that prevents building near biter nests. I am also using HeroTurrets which is why in the screenshot a bit further down the turrets have ranks. It gives them a bit more damage and a bit more range every time they level up.

I get that I can't build near biter nests, but if my base is within that range when the biters expand closer to my base my stuff starts to get auto deconstructed? Why? I can't have defences up if they just get automatically taken down just because the biters get closer.

https://imgur.com/a/7uX0r6X

Some of the turrets are still there, but some of the other ones have been taken down. I'm assuming because the range of the turrets that got removed are too big, Rampant begins to remove them. If it is Rampant that is causing this, how come there are no warnings in chat?

Are you playing with AAI Programmable Vehicles mod?

I am indeed but I really should uninstall it because I don't use it.

That's a very quick and to the point statement so I'm going to guess that's the culprit?

Oh but I lose the AI Vehicles, ok acceptable compromise if that is the culprit.

You can tell mod author, that you don't like such a feature of that mod and ask if it can be made optional via mod setting. IMHO feature is not good and there's no logics under it. There are better ways (haha, I did one).

That's fair, I'll probably leave it for now, I've just disabled that mod, I don't really use it anyway.

Sorry for assuming it was Rampant!

Veden put this issue in FAQ here.
Players report this issue for Rampant very often because Rampant expansion tactics provokes nests growth near buildings. And no one expects this punishment from AAI Programmable Vehicles mod. Vanilla logics sends builders to free chunks only and doesn't expand existing enemy bases.