Hey Artistical -
This looks like a unwrap issue in the lightmap. Could you post a screenshot of your lightmaps for a few of the offending meshes?
And in the meantime, take a look at this article on setting up your UVs for Lightmapping. It is for Maya and UDK, but the information provided can work in any modeling program and UE4:
UDK: Lightmap UV Layout Techniques and How to Create a Second UV Channel in Maya
Thank You
Eric Ketchum