I have weird “stains” after baking the light on my custom meshes when they have a round shape:
I’ve been trying about everything (in the lightbaking menu) but nothing seems to solve this problem (AO on and off, AO parameters, final gather yes/no, Atlas size, Directional mode)
I do generate lightmap UVs on import (I’ve tried all sort of settings there as well)
Try to bring in your own custom UV maps and avoid generating lightmap UV automatically within Unity unless it’s a massive building for instance. Also the atlas size has no influence on the baking res. The texel resolution does. In the end we mostly avoid AO baking in Unity as you end up spending your life baking. If you work on a lot of different platforms I would even suggest avoiding baking lights in Unity altogether but the alternatives can be painful as well. It all depends on your workflow and the complexity of the project I guess.