Our animations were not working with our dispatch queue. I boiled it down to a simple test case. However, the test case works perfectly as expected so there is another problem that is happening. This code makes a view oscillate back and forth.

RFViewController.m

- (void)viewDidAppear:(BOOL)animated
{
  [super viewDidAppear:animated];
  [self move];
}

- (void)move
{
  static BOOL flipFlop;
  dispatch_queue_t computeQueue = dispatch_queue_create("worker.queue", NULL);
  dispatch_async(computeQueue, ^{
    CGPoint point = [self computePoint:flipFlop];
    flipFlop = !flipFlop;
    dispatch_sync(dispatch_get_main_queue(), ^{
      [self moveTo:point];
    });
  });
}

- (CGPoint)computePoint:(BOOL)flipFlop
{
  return flipFlop ? CGPointMake(300, 300) : CGPointMake(10, 10);
}

- (void)moveTo:(CGPoint)point
{
  CGRect targetFrame = self.graphicView.frame;
  targetFrame.origin = point;
  
  [UIView animateWithDuration:1
    animations:^{
      self.graphicView.frame = targetFrame;
    }
    completion:^(BOOL finished) {
      [self move];
    }
   ];
}