iOS SpriteKit headache; runAction:completion: not triggering completion block

Question

I'm looking to make a pause on touch for a SprintKit game. When the game is paused a label is shown with PAUSE as text until the user touchUp the screen again to un-pause. When the game un-pauses a countdown from 3 will be displayed prior to the scene being ran again.

it appears that line 7 ([_pauseLabelNode setText:@"2"];) is never triggered by the animation completing, which is strange as I use runAction:completion: elsewhere in the code and that works fine! In order to make this work do i need to over-inflate this by setting up an operation queue in order to control the animation sequence? or have I just made a mistake but am blind to it?

Here is what I have so far:

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    if ([self isPaused]) {
        [_pauseLabelNode setText:@"3"];
        [_pauseLabelNode setScale:1.0];
        [_pauseLabelNode runAction:[SKAction scaleTo:0.0 duration:1.0] completion:^{
        [_pauseLabelNode setText:@"2"];
        [_pauseLabelNode setScale:1.0];
        [_pauseLabelNode runAction:[SKAction scaleTo:0.0 duration:1.0] completion:^{
            [_pauseLabelNode setText:@"1"];
            [_pauseLabelNode setScale:1.0];
            [_pauseLabelNode runAction:[SKAction scaleTo:0.0 duration:1.0] completion:^{
                [_pauseLabelNode setScale:1.0];
                [self setPaused:NO];
                [_pauseLabelNode setText:@"GO"];
                [_pauseLabelNode runAction:[SKAction scaleTo:0.0 duration:0.5]];
            }];
        }];
    }];
} else {
    _pauseLabelNode = [SKLabelNode labelNodeWithFontNamed:@"Papyrus"];
    [_pauseLabelNode setHorizontalAlignmentMode:SKLabelHorizontalAlignmentModeCenter];
    [_pauseLabelNode setPosition:CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame))];
    [_pauseLabelNode setFontSize:48.0f];
    [_pauseLabelNode setZPosition:100];
    [_pauseLabelNode setText:@"Pause"];
    [self addChild:_pauseLabelNode];
    [self setPaused:YES];
    [_pauseLabelNode runAction:[SKAction sequence:@[[SKAction scaleTo:1.5 duration:0.1], [SKAction scaleTo:1.0 duration:0.1]]]];
}