Hey Kensey! I might be able to shed some light on the problem (funny joke, right?). You are always going to get light map seams on objects where the UV shells are mapped diagonally. You have to make sure your Lightmap seams fall between pixels to ensure a perfect seamless light bake. This means your UV shells are going to…
If you could upload that mesh and it's normals, I'll be willing to take a look at it. Also, have you done a bake lighting without normals on it? (I.e. just diffuse.) Just to troubleshoot anything about normals, because I've encounter such before.