I fear it's rather an issue in the way Sweet Home 3D attempts to cut the ground with the room. Sometimes it doesn't work well. I tried so many times to fix this problem, that I'm not sure there's a better solution. Maybe moving a little the corners of the room where you see the issue could help. Anyway, no need to export many times your design to check a fix, because you should see this flickering in Sweet Home 3D too.