Either the lightmap resolution is too low (unlikely), or the lightmap UVs are incorrect (most likely).
You should make a separate UV channel for lightmaps, and set that to be used in the Static Mesh asset editor.
Either the lightmap resolution is too low (unlikely), or the lightmap UVs are incorrect (most likely).
You should make a separate UV channel for lightmaps, and set that to be used in the Static Mesh asset editor.