I’m guessing a bit here but if the gap is too big and the shadow from the gap over the door is bleeding around to the wall then it’s most likely that you haven’t separated the polygons inside the gap from the wall polygons. Maybe this image helps (I made it a while ago for unreal 3 but it is still valid)
For the couches: We always have these problems with old high poly objects. It is really hard to make a good lightmap for a high poly object. Best is often to just bake a new low poly object off the high poly old vray asset.
Despite the general problems it might just be that your lightmap resolution is too low for the couch and the shadow is bleeding from one uv chart to another. (a too low lightmap resolution could also be caused by texture streaming issues but the scene seems to be small and not having any streaming issues.) Unreal is pretty good in rearranging the lightmap uv’s. You could try to reshuffle the uv charts in the mesh browser (built settings just after the material section). Use 1 as source and target uv channel, set the minimum resolution to maybe 128 or 256 and hit “apply”. Then make sure you increase the lightmap resolution further down in the static mesh settings as well.