tvos - remembersLastFocusedIndexPath not working on UICollectionView -

i have collection view standard horizontal layout. upon presenting view controller , dismissing it, collection view reset focus first cell, though last focused cell not one.

i've set

self.collectionview.rememberslastfocusedindexpath = yes; 

what's weird happens when push view controller on navigation controller.

so if

[self.navigationcontroller pushviewcontroller:controller animated:yes]; 

and dismiss, rememberslastfocusedindexpath not work properly.

however, if i:

[self presentviewcontroller:controller animated:yes completion:nil]; 

then works expected.

any idea why wouldn't work via navigation controller?

what worked me ensuring preferredfocusview on viewcontroller collection view:

override weak var preferredfocusedview: uiview? {     return collectionview } 

after rememberslastfocusedindexpath seems work.