Are you using screen space ambient occlusion (SSAO) or distance field ambient occlusion (DFAO)? Have you checked the attenuation radius of all lights in the scene? it may also be source radius (which if it’s set to 0, is actually the default of 20 so could still be affecting things); setting it between 0 and 20 may do something to correct it, or above 20.
Do all the objects have cast dynamic shadows enabled?