Static Batching causing Lightmaps to display artifacts?

(Unity 5, Win7 x64) I have a scene - basically architectural visualization - where the vast majority of the objects are static and marked as such. Once I'd gotten into optimizing the scene, I turned on Static Batching (because 99% of the scene is static) and noticed that while it helped a lot with draw calls, I noticed that suddenly my lightmaps were displaying artifacts in a build (but not at runtime in the editor)

Both of these screen shots are from web builds running in Firefox:

I'm seeing these anomalies all over the building and on all objects. My question is: Is there a setting I'm missing somewhere, is this expected behavior, or is this a bug? Any ideas would be appreciated.