Rotation around different anchorPoint and position makes image jump to new position first - objective-c

Question

I'm doing a rotation animation on a view and want it to rotate around the view's center X and bottom Y. I change the anchorPoint and position of the layer and run the animation. Here's my code:
- (void)viewDidLoad {
[super viewDidLoad];
_imageView = [UIImageView newAutoLayoutView];
_imageView.image = [PCImage imageNamed:#"Umbrella"];
[self.view addSubview:_imageView];
[_imageView autoAlignAxisToSuperviewAxis:ALAxisVertical];
[_imageView autoPinEdgeToSuperviewEdge:ALEdgeBottom];
}
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
CGPoint newPosition = CGPointMake(CGRectGetMidX(_imageView.frame), CGRectGetMaxY(_imageView.frame));
NSLog(#"frame %#, new position %#", NSStringFromCGRect(_imageView.frame), NSStringFromCGPoint(newPosition));
_imageView.layer.anchorPoint = CGPointMake(.5, 1.0);
_imageView.layer.position = newPosition;
[UIView animateKeyframesWithDuration:2.0 delay:2.0 options:UIViewKeyframeAnimationOptionCalculationModeLinear | UIViewKeyframeAnimationOptionAutoreverse | UIViewKeyframeAnimationOptionRepeat animations:^{
[UIView addKeyframeWithRelativeStartTime:0.0 relativeDuration:.1 animations:^{
_imageView.transform = CGAffineTransformMakeRotation(M_PI / 64);
}];
} completion:nil];
}
edit
The rotation is working, but the view 'jumps' upward to a new position first, where the view's bottom is now where the view's center Y was when first laid out. I thought changing the anchorPoint and updating the position would prevent the jumping. The view is pinned to the superview's bottom edge, and center X to the superview's center X in autolayout, if that might matter. Any ideas?
edit2
I've read other good posts on this like the following but I must be missing something..
Scale UIView with the top center as the anchor point?

Answer 1

I ended up changing the view to not use autolayout after reading this post:
Adjust anchor point of CALayer when autolayout is used
Looks like transforms and autolayout aren't designed to work well together.
_imageView = [UIImageView new];
_imageView.image = [PCImage imageNamed:#"Umbrella"];
_imageView.frame = CGRectMake(0, kScreenHeight - _imageView.image.size.height, _imageView.image.size.width, _imageView.image.size.height);
[self.view addSubview:_imageView];
At some point hoping to experiment with other ideas in that post.