Hi ,
Can you try building the lighting in Production mode if you’ve not already done so? Preview and any mode lower than Production can generate the light bleed you’re seeing, in most cases. If that doesn’t solve the issue then it may be that you need to revisit your lightmaps and set the hard edges to snap on the grid in the UV space for your hard edges. The grid will need to be set up to the lightmap resolution you’re targeting.
You can find more information about lightmaps here in this forum thread. There is a lot of information being discussed that can be helpful. Modular Asset Lighting Problem - Rendering - Epic Developer Community Forums
Thank you!