When baking using Corona 1.7, I get weird patches of noise. I never experienced this in 1.5.2. I’m doing fast previews (10% noise level limit and 0.65 denoise amount), but I still think it shouldn’t be this noticable and such a big difference between smooth and noisy areas?
Not sure if that has any relation to your problem, but can you check if new light solver is disabled in render setup>performance tab?
For this example, it was off. I’ve turned it on and the new renders seem to have the exact same thing. The only light is an HDR image.
Anyone? It gets better if I set the noise level limit to 2 or 3, but I don’t have the time to render a lot of large lightmaps with those settings.
Guesswork only without scene:
- The scene renders normally when not baking?
- Have you tried to bake this with 1.6.x?
- Are there portals? If yes, have you tried without?
- Have you checked geometry? (thickness/normals/scale/double faces…)
- Do all bake elements look like this?
If the problem persists you may open a ticket and send the scene for investigation.
Good Luck
Can you try changing Random sampler in devel/debug settings from “New Improved” to “Stratified” and see if it helps?
Here is how to access devel/debug settings: https://coronarenderer.freshdesk.com/support/solutions/articles/12000021288
Please do not touche anything else in there. 
If that helps, let us know, and send us the scene if possible.
Sorry, missed all the answers here. I solved it by adding portals. I haven’t had to use them before, though, that’s why I didn’t think of it to begin with.