Quoted by Uhfgood:
Interesting, it looks like you're doing bullet-to-bullet collisions... it looks like the "row" of bullets means that a bullet had collided with another one at the same position, and then of course it's set back to where it didn't collide...
No, that's not at all what I was doing. I was firing the bullets at the wall while sweeping left. The bullets did not hit each other.