If you have auto layout turned on, you would need to turn it off.
But it doesn't seem to your problem here as per your description.
I would do the following to re-adjust to the center as it scales:
CGPoint cP = _favButton.center;
[UIView animateWithDuration:2.0 animations:^
{
_favButton.transform = CGAffineTransformMakeScale(0.5, 0.5);
_favButton.layer.position = cp;
}
completion:^(BOOL finished)
{
[UIView animateWithDuration:2.0 animations:^
{
_favButton.transform = CGAffineTransformMakeScale(1, 1);
_favButton.layer.position = cp;
}];
}];
Hope this helps.