iPad 10.5 in Split Screen (equal width) lag on rotation

[xapp]

I have sort of Photos app layout https://drive.google.com/open?id=0Bycu0Xewdx_XLTRlT21mYUhfRGc

It works fine, except the case when app in landscape, in equal Split Screen, on rotation to portrait (and back) there is a crazy lag/fps drop.

iOS 11 beta 9.

Any ideas?