Mesh throwing 'Overlapping UVs' error

Make sure that you’ve got your lightmap coordinate index set to 1. So far, you’ve shown that you’ve set the build settings (for auto-generated lightmap UVs) and that you’re looking at UV 1 for the lightmap UV.

Under the static mesh settings tab you’ll find Lightmap Coordinate Index. This needs to be set to 1 so that it uses the correct UV. The build settings you showed are only used for generation.