UICollectionView Crashes on Scroll (lldb) - ios

Question

I'm trying to add a uicollectionview as a subview into a View, called CollectionSpace, by calling it from Storyboard.
UIViewController *CollectionVC =[self.storyboard instantiateViewControllerWithIdentifier:#"CollectionVC"];
CollectionVC.view.frame = CGRectMake(CollectionSpace.frame.origin.x-276, CollectionSpace.frame.origin.y-87, CollectionSpace.frame.size.width+2, CollectionSpace.frame.size.height-2);
[CollectionSpace addSubview:CollectionVC.view];
The storyboard has a Collection View where the delegate and Source, as the uicollectionview have been linked to the owner view controller. Here is the code:
#import "ViewController.h"
#interface ViewController ()
#property (nonatomic, strong) IBOutlet UICollectionView *collectionView; //linked
#end
#implementation ViewController
- (void)viewDidLoad
{
self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc] init];
_collectionView=[[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:layout];
[_collectionView setDataSource:self];
[_collectionView setDelegate:self];
[_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:#"cellIdentifier"];
[_collectionView setBackgroundColor:[UIColor redColor]];
[self.view addSubview:_collectionView];
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 100;
}
// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
cell.backgroundColor=[UIColor greenColor];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
return CGSizeMake(150, 150);
}
So this works fine, it loads the uicollectionview and I can see the cells. The problem comes when I scroll. Once I scroll, the app crashes. (lldb)
I tried to call differently by importing the view controller and initiate it like this:
UICollectionViewFlowLayout *aFlowLayout = [[UICollectionViewFlowLayout alloc] init];
[aFlowLayout setItemSize:CGSizeMake(200, 140)];
[aFlowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];
ViewController *CollectionVC = [[ViewController alloc]initWithCollectionViewLayout:aFlowLayout];
But the uicollectionview doesn't show up.
Any idea what could be causing the crash?