The UVs look ok for this here. Looking at your previous images, the lightmap resolution is set to 32, which seems low for an object this size. This could cause some of the artifacts you see in the corners. Try increasing the lightmap resolution and stopping when you get to a good resolution without artifacts. I wouldn’t go too high with resolution if it were for a game, but something more archvis oriented should be OK I think since gameplay isn’t the biggest factor vs the render.