Huge Lightmap Problem!!

Hi.

I have got a massive problem with Lightmapping. I have a huge scene, and last night I have baked the Lightmaps for my directional light. Besides that it took 6 hours, since it’s finished it started giving me an error EVERY SECOND:

“Lightmap index must be less than 256”

After I googled the Problem (without any Solution) I decided to just clear the Lightmap so that I can work with Unity again. (Because of the massive amount of Error messages it gave me, Unity was very, very laggy. It was UNUSABLE.) So after a few minutes of waiting for Unity to react, it cleared the Lightmap. But after cleaning the Lightmap, I STILL GET THE ERROR! This is just driving me crazy. I have (re-)started Unity many times, I restarted my PC, but it still DOESN’T WORK- Please Help me! I’ve spending at least 3 months on my Project, and now I can’t work on it any longer. This is frustrating. Does anyone know how to solve this Problem???

any objects you set to light map static change back to static

This saved me:
I had the same issue of light mapping index after baking a complex scene…
Drove me really nuts, until this solution worked for me.