Grid-grid collision bug

Main.as

package
{
	import net.flashpunk.*;
	import net.flashpunk.graphics.*;
	import net.flashpunk.masks.*;
	
	import flash.display.*;
	
	[SWF(width = "640", height = "480", backgroundColor="#000000")]
	public class Main extends Engine
	{
		public var e1:Entity;
		public var e2:Entity;
		
		public var g1:Grid;
		public var g2:Grid;
		
		public function Main () 
		{
			super(640, 480, 60, true);
			
			createEntity(120, 120, 40);
			
			e1 = createEntity(110, 165, 30);
			
			createEntity(320, 120, 40);
			
			e2 = createEntity(325, 165, 30);
			
			FP.console.enable();
		}
		
		private function createEntity (x:Number, y:Number, gridSize:Number):Entity
		{
			var e:Entity = new Entity;
			e.x = x;
			e.y = y;
			e.type = "solid";
			
			var g:Grid = new Grid(gridSize*2, gridSize*2, gridSize, gridSize);
			g.setTile(0, 0);
			g.setTile(1, 1);
			e.mask = g;
			
			var t:Tilemap = new Tilemap(new BitmapData(gridSize, gridSize, true, 0xFFFFFFFF), gridSize*2, gridSize*2, gridSize, gridSize);
			t.setTile(0, 0, 0);
			t.setTile(1, 1, 0);
			t.alpha = 0.5;
			e.graphic = t;
			
			FP.world.add(e);
			
			return e;
		}
		
		public override function update ():void
		{
			super.update();
			
			//e1.x = FP.world.mouseX;
			//e1.y = FP.world.mouseY;
			
			Tilemap(e1.graphic).color = (e1.collide("solid", e1.x, e1.y)) ? 0xFF0000 : 0x00FF00;
			Tilemap(e2.graphic).color = (e2.collide("solid", e2.x, e2.y)) ? 0xFF0000 : 0x00FF00;
		}
	}
}