Why does the physics joint stop working if the object will move out of the view?

Question

I have a construction crane that has a joint with an object. The joint works fine if the crane is stationary.

But I added the ability for the crane to move left to right and whenever the crane is about to leave the view with the object, the object hits the edge of the screen and gets stuck while the crane keeps going. The joint also stops working even after the crane has come back to the view.

Here's an image. The yellow line at the top represents the path the hook follows forever. It goes left to right. The gold block that's around the blue rectangle is what's getting stuck. That's the block that's originally jointed with the crane's gray hook. But when the hook moves to right side of the view, the gold block hits the edge of the screen and stays there forever.

What doesn't make sense to me is that the edge of the view has a category bit mask of 0 while the gold block is at 64. In other levels, the gold blocks NEVER collide with the edge. But here when the crane moves to the edge, the gold block collides with the edge and gets stuck. As you can see, the joints are still there based on the light blue physic lines.

This is the code of the joint being called from the scene and configuring it. Like I said, joint works fine if the hook is stationary.

craneBase.alpha = 0
let path = CGMutablePath()
path.move(to: CGPoint(x: craneBase.position.x, y: craneBase.position.y))
 path.addLine(to: CGPoint(x: craneBase.size.width - 100, y: craneBase.position.y + 10))
 path.addLine(to: CGPoint(x: craneBase.position.x, y: craneBase.position.y))
 craneHook.initializeMovingJoint(withObject: childNode(withName: "HookedObject") as! SKSpriteNode)
 hook.run(SKAction.repeatForever(SKAction.follow(path, asOffset: false, orientToPath: false, duration: 10)))
 physicsWorld.add(craneHook.joint)

This is the code of the crane's hook class that adds the joint to the block.

private func initHook() {
    self.hookSize = CGSize(width: 10, height: 10)
    self.physicsBody = SKPhysicsBody(rectangleOf: hookSize)
    self.physicsBody?.categoryBitMask = PhysicsBit.none
    self.physicsBody?.isDynamic = false
    self.physicsBody?.affectedByGravity = false
}

//Creates the joint between the object and the hook
func initializeJoint(withObject object: SKSpriteNode) {
    initHook()
    hookedObject = object
    jointAnchor = CGPoint(x: self.anchorPoint.x, y: self.anchorPoint.y)

    joint = SKPhysicsJointFixed.joint(withBodyA: physicsBody!, bodyB: hookedObject.physicsBody!, anchor: jointAnchor)
    doesHaveHookedObject = true
}

And the gold block's settings are assigned from the scene editor to a category mask of 64. I've tested the gold blocks and they don't collide with the edge. I'm not sure why it collides with the edge while moving.

Answer 1

I realized it was not working because the joint and the physicsWorld had the same category bit mask. Even though the gold block had a different bit mask, it was part of the joint and thus collided with the same category bit mask as none.