Yeah, I've seen a multitude of reasons for the black lines and several ways to try and fix it. I went through every solution I could find and it didn't help mine at all. Spent hours on it. For me, it turns out my tiles were sitting like 1.499883, 1.503423 instead of 1.5, 1.5 and that's what was causing it for the small group of tiles it was happening for in my game.