It's the conveyor in the top left corner. I don't know why, it just is. I tried removing random things, and I started with the corners. So for some reason, it's disabling the spikes in the room. Also, don't use a moving platform in the top left corner either; it both disables the spikes and moves right a few squares instantly! They're the only two things I found that disable spikes, though - you'll probably have to change it so the top left tile is a wall tile or something.