UIAttachmentBehaviour works incorrectly - objective-c

Question

I would like to drag one UIView, and have it move the position of other views attached to it as if they were all attached via string. I added two attached behaviours, one between my views and one between view which allowed to dragging and anchor point. And it works. But my problem is that my views continue to move even after gesture ended. My current result:
What do i do wrong?
Here is my code:
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.views = [[NSMutableArray alloc] init];
self.v2 = [[UIView alloc] initWithFrame:CGRectMake(50, 450, 200, 200)];
self.v2.backgroundColor = [UIColor colorWithRed:34.0f/255.0f green:167.0f/255.0f blue:240.0f/255.0f alpha:1.0];
[self.view addSubview:self.v2];
self.v1 = [[UIView alloc] initWithFrame:CGRectMake(150, 450, 200, 200)];
self.v1.backgroundColor = [UIColor colorWithRed:210.0f/255.0f green:82.0f/255.0f blue:127.0f/255.0f alpha:1.0];
[self.view addSubview:self.v1];
self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
self.gravity = [[UIGravityBehavior alloc]initWithItems:#[self.v1, self.v2]];
self.gravity.gravityDirection = CGVectorMake(0.0, 0.0);
[_animator addBehavior:_gravity];
_collision = [[UICollisionBehavior alloc]initWithItems:#[self.v1]];
_collision.collisionDelegate = self;
_collision.translatesReferenceBoundsIntoBoundary = YES;
[_animator addBehavior:_collision];
UIDynamicItemBehavior *itemBehaviour = [[UIDynamicItemBehavior alloc] initWithItems:#[self.v1]];
itemBehaviour.elasticity = 0.6;
itemBehaviour.allowsRotation = NO;
[_animator addBehavior:itemBehaviour];
UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handlePan:)];
[self.v1 addGestureRecognizer:gesture];
UIAttachmentBehavior *attach = [[UIAttachmentBehavior alloc] initWithItem:self.v2 attachedToItem:self.v1];
attach.damping = 0.50f;
attach.length = 150.0f;
attach.frequency = 1.9;
[_animator addBehavior:attach];
}
-(void)handlePan:(UIPanGestureRecognizer *)gesture
{
CGPoint touchPoint = [gesture locationInView:self.view];
static float y ;
if (gesture.state == UIGestureRecognizerStateBegan) {
self.attachmentBehavior = [[UIAttachmentBehavior alloc] initWithItem:self.v1 attachedToAnchor:touchPoint];
self.attachmentBehavior.damping = 0.50f;
self.attachmentBehavior.frequency = 1.9;
[_animator addBehavior:self.attachmentBehavior];
y = self.v1.center.y;
} else if (gesture.state == UIGestureRecognizerStateChanged ) {
CGPoint center = self.v1.center;
center.x = touchPoint.x;
center.y = y;
self.attachmentBehavior.anchorPoint = center;
} else if (gesture.state == UIGestureRecognizerStateEnded) {
[self.animator removeBehavior:self.attachmentBehavior];
}
}