Static emissive baked lightmap issue

I have a static plane with an emissive material shining into a room made of cubes. When I bake the lightmap I get these weird effects that look like the floor and walls have wrinkles in them. The floor is only made of one default unity cube so I don’t think it’s a stitching issue. Is there a way to increase emissive light quality maybe?

Disable “Compression” option from the rendering settings window

Don’t forget that all indirect lights (sky light, area light, emissive materials) has much more noise compare to the direct lights(directional, spot, point) so you must increase the Indirect Samples from the rendering settings window

Also you can use fake indirect lighting simulation: