Ipad 2 iOS 4.3.1 => 9.1 leads to Infinite Loop
Device: Ipad 2 64GB
Current iOS: 4.3.1
Ipad belongs to my friend's father, he has no idea about software updates etc so his ipad is still running ancient iOS. He tried to update iPad via iTunes and that led to unknown error 9 and iPad's gotten stuck at infinite iTunes loop. The only thing that helped was redsn0w tool for breaking iTunes loop, after that iPad was working ok. When I tried to update it one more time it returned same result.
Question is: Error 9 seems to be USB connection failure, but iPad synchronizes without problems while on iOS 4.3.1. Also tried on 3 different laptops (2 x Mac OS and one Windows), same result.
Is there any way to finally update iPad at least to iOS 7 or 8 if not 9?
iPad 2, iOS 4.3.1