So.. i'm having the lightmap artifacts issue too! I've read that some people has solved making their own Lightmap parameters and increase the pushoff value (i've tried to increased till the maximum) and still i haven't solved the issues.. I've tried almost all the combination of the parameters and nothing.. still having that issue. Now i've noticed an interesting thing.. I've attached 3 screenshot to that thread. One screenshot is with the lamp lightmapped till the end with the black patches and artifacts on that.. another screenshot is with the lamp that looks a little bit "dark" and another one is just.. "fine".. Now.. The screenshot with the black patches is the result if i make the baking.. the screenshot with the lamp being darker.. is if i DO NOT bake the lamp.. and the last one is i restart unity.. and the first steps of the lightmapping starts..and it seems that the lamp change from the dark/non-lightmapped colors to the new correctly lightmapped colors.. but while the baking go forward probably something goes wrong and when the bake is finished the result is the lamp + artifacts.. That should be an interesting thing for the Unity devs.. cause there are clearly one specific step of the baking that are doing something wrong and not only.. maybe are literally ruin the already well-lightmapped lamp.. I mean.. the interesting thing here is that for just a MOMENT the lamp is well-lightmapped but after that the bake goes forward.. it happens the issue. Hope that will be useful.. i don't know what else i can do to solve this issue so i'm hoping for some Unity fixes on the upcoming releases.