Hi GrafithZ,
What is your light map resolution? It looks to me like the very narrow uv islands are to small. Try cranking your lightmap resolution for this asset up to 2k as a test. If it lights okay, they you can assume that your uvs are not efficient enough and need a better layout. You can then reduce the light map resolution to a more reasonable size and re-do your layout more efficiently. If this is the case then scale up the very small islands so that they cover more than just one or two pixels of the light map.
If you are looking for more information about laying out good lightmap uv’s then I would recomend these pages: UDK Lightmap Common Problems, Errors and Solutions
https://docs.unrealengine.com/latest/INT/Engine/Content/Types/StaticMeshes/LightmapUnwrapping/index.html#contiguousuvsandpadding
Best wishes,
Matt Cooke