Patches more shiny than standard geometry?

Game Modding | Call of Duty: Black Ops 3 | Radiant

ModmeBot:

Thread By: Exofile

I'm trying to curve off my corners, but end up seeing them a bit wrongly lit up.

As you can see in the 4 corners, whether they're inwards or outwards they are lit up differently, and offer a rather higher reflection than the rest. Any particular reason as to why this is, and is there a way I can fix this?