Hi! I've discovered little bug and recently found fix for it:).
I have grid view 2x2 and 5 items in it. If i scroll to second page (only half page) and rotate, the new position(originScroll) is calculated incorrectly.
Here's fix, that works for me:
originScroll = CGPointMake(MIN(pageX * pageSize.width,self.contentSize.width-pageSize.width),MIN(pageY * pageSize.height,self.contentSize.height-pageSize.height));